Systems and methods for controlling negative pressure therapy with fluid instillation therapy

ABSTRACT

Systems, apparatuses, and methods for providing negative pressure with instillation fluids to a tissue site are disclosed. Some embodiments are illustrative of an apparatus or system for delivering negative-pressure and/or therapeutic solution of fluids to a tissue site, which can be used in conjunction with sensing properties of fluids extracted from a tissue site and/or instilled at a tissue site. For example, a system may comprise a tissue interface adapted to be coupled to a source of instillation fluid and a dressing interface having a therapy cavity that includes a pH sensor, a humidity sensor, a temperature sensor, and a pressure sensor embodied on a single pad within the dressing interface to provide data indicative of acidity, humidity, temperature and pressure at the tissue site. Such apparatus may further comprise algorithms for processing such data for detecting leakage and blockage conditions as well as providing information relating to the progression of healing of wounds at the tissue site. An illustrative method may comprise disposing the tissue interface at the tissue site and the therapeutic cavity in fluid communication with the tissue interface. The method may further comprise instilling fluid to the therapy cavity and then sensing the pressure, humidity, temperature, and the pH of the fluids adjacent the tissue interface. The method may further comprise determining various flow characteristics of the system by using a processing element electrically coupled to the sensors for transmitting property signals from the sensors to a controller configured to assess the property signals in order to identify the flow characteristics.

RELATED APPLICATION

This application claims the benefit, under 35 USC § 119(e), of thefiling of U.S. Provisional Patent Application Ser. No. 62/617,521,entitled “SYSTEMS AND METHODS FOR CONTROLLING NEGATIVE PRESSURE THERAPYWITH FLUID INSTILLATION THERAPY,” filed Jan. 15, 2018, which isincorporated herein by reference for all purposes.

TECHNICAL FIELD

The invention set forth in the appended claims relates generally totissue treatment systems and more particularly, but without limitation,to systems and methods for providing negative-pressure therapy withfluid instillation therapy and sensing properties of wound exudatesextracted from a tissue site.

BACKGROUND

Clinical studies and practice have shown that reducing pressure inproximity to a tissue site can augment and accelerate growth of newtissue at the tissue site. The applications of this phenomenon arenumerous, but it has proven particularly advantageous for treatingwounds. Regardless of the etiology of a wound, whether trauma, surgery,or another cause, proper care of the wound is important to the outcome.Treatment of wounds or other tissue with reduced pressure may becommonly referred to as “negative-pressure therapy,” but is also knownby other names, including “negative-pressure wound therapy,”“reduced-pressure therapy,” “vacuum therapy,” “vacuum-assisted closure,”and “topical negative-pressure,” for example. Negative-pressure therapymay provide a number of benefits, including migration of epithelial andsubcutaneous tissues, improved blood flow, and micro-deformation oftissue at a wound site. Together, these benefits can increasedevelopment of granulation tissue and reduce healing times.

There is also widespread acceptance that cleansing a tissue site can behighly beneficial for new tissue growth. For example, a wound can bewashed out with a stream of liquid solution, or a cavity can be washedout using a liquid solution for therapeutic purposes. These practicesare commonly referred to as “irrigation” and “lavage” respectively.“Instillation” is another practice that generally refers to a process ofslowly introducing fluid to a tissue site and leaving the fluid for aprescribed period of time before removing the fluid. For example,instillation of topical treatment solutions over a wound bed can becombined with negative-pressure therapy to further promote wound healingby loosening soluble contaminants in a wound bed and removing infectiousmaterial. As a result, soluble bacterial burden can be decreased,contaminants removed, and the wound cleansed.

While the clinical benefits of negative-pressure therapy andinstillation therapy are widely known, improvements to therapy systems,components, and processes may benefit healthcare providers and patients.

BRIEF SUMMARY

New and useful systems, apparatuses, and methods for instilling fluid toa tissue site in a negative-pressure therapy environment are set forthin the appended claims. Illustrative embodiments are also provided toenable a person skilled in the art to make and use the claimed subjectmatter. Some embodiments are illustrative of an apparatus or system fordelivering negative-pressure and therapeutic solution of fluids to atissue site, which can be used in conjunction with sensing properties ofwound exudates extracted from a tissue site. For example, an apparatusmay include a pH sensor, a humidity sensor, a temperature sensor and apressure sensor embodied on a single pad proximate the tissue site toprovide data indicative of acidity, humidity, temperature and pressure.Such apparatus may further comprise an algorithm for processing suchdata for detecting leakage and blockage as well as providing informationrelating to the progression of healing of wounds at the tissue site.

In some embodiments, for example, a system for controlling negativepressure therapy with fluid instillation therapy using properties offluids at a tissue site wherein the system may comprise a tissueinterface adapted to be disposed at a tissue site and further adapted tobe coupled to a source of instillation fluid. The system may furthercomprise a dressing interface adapted to couple a source ofnegative-pressure to the tissue interface, wherein the dressinginterface comprises a housing having a therapy cavity including anopening configured to be disposed in fluid communication with the tissueinterface, and a negative-pressure port adapted to fluidly couple thetherapy cavity to the source of negative-pressure. The dressinginterface may further comprise a pressure sensor mounted to the housingin fluid communication with the therapy cavity and configured to sensethe pressure of the fluids adjacent the tissue interface duringinstillation of liquids to the tissue interface, a humidity sensormounted to the housing in fluid communication with the therapy cavityand configured to sense the humidity of the fluids adjacent the tissueinterface during instillation of liquids to the tissue interface, and atemperature sensor mounted to the housing in fluid communication withthe therapy cavity and configured to sense the temperature of the fluidsadjacent the tissue interface during instillation of liquids to thetissue interface. The dressing interface may further comprise aprocessing element electrically coupled to the pressure sensor, thehumidity sensor, and the temperature sensor for receiving propertysignals indicative of the pressure, humidity, and temperature, theprocessing element being configured to determine flow characteristics ofthe system. In some embodiments, the therapy cavity may further comprisea vent port adapted to fluidly couple the therapy cavity to a source ofpositive-pressure.

In some embodiments, the system may further comprise a controllerconfigured to receive the property signals from the processing elementand to assess property readings reflective of the property signals toidentify the flow characteristics of the system. The system may furthercomprise a transmitter configured to transmit the property signals tothe controller. The system may further comprise an instillation pumpconfigured to provide instillation fluid to the tissue interface, and asensor electrically coupled to the controller and adapted to measure aninstillation pump pressure and an instillation duty cycle provided bythe instillation pump. The controller may be configured further toassess the property readings and provide an alarm identifying a blockagestate condition as one of the flow characteristics flow characteristicswhen the instillation pump duty cycle increases while the humidityremains substantially the same. The controller may be configured furtherto assess the property readings and provide an alarm identifying a fluidleak state as one of the flow characteristics flow characteristics whenthe instillation pump duty cycle and the humidity remain substantiallythe same. The controller may be configured further to assess theproperty readings and provide an alarm identifying a dressing fill stateas one of the flow characteristics when the humidity increases to apredetermined target threshold humidity.

In some embodiments, the dressing interface may further comprise a pHsensor mounted to the housing in fluid communication with the therapycavity and configured to sense the pH of the fluids adjacent the tissueinterface during instillation of liquids to the tissue interface. Theprocessing element may be electrically coupled to the pH sensor forreceiving property signals including a property signal indicative of thepH, wherein the processing element may be configured to assess thehealth characteristics of the tissue site. The controller may be furtherconfigured to receive the property signals indicative of the pH from theprocessing element and to assess property readings reflective of theproperty signals to identify the health characteristics of the tissuesite. The processing element may be further configured to transmit theproperty signals indicative of the pH to the controller. The healthcharacteristics of the system may include a wound progression statewithin the system, and the controller may be configured to provide analarm indicative of the wound progression state based on the propertysignals.

Some embodiments are illustrative of a method for utilizing a system forproviding negative pressure with fluid instillation therapy andassessing properties of liquids at the tissue site, wherein the systemcomprises a tissue interface and a dressing interface having a housingincluding a therapy cavity. In some embodiments, the method may comprisedisposing the tissue interface at the tissue site, the tissue interfaceadapted to be coupled to a source of instillation fluid and disposingthe therapy cavity in fluid communication with the tissue interface, thetherapy cavity adapted to be coupled to a source of negative pressure.The method may also comprise providing instillation fluid from thesource of instillation fluid to the therapy cavity. In some embodiments,the method may further comprise sensing pressure of the fluids adjacentthe tissue interface during instillation of liquids to the tissueinterface using a pressure sensor mounted to the housing in fluidcommunication with the therapy cavity, sensing humidity of the fluidsadjacent the tissue interface during instillation of liquids to thetissue interface using a humidity sensor mounted to the housing in fluidcommunication with the therapy cavity, and sensing temperature of thefluids adjacent the tissue interface during instillation of liquids tothe tissue interface using a temperature sensor mounted to the housingin fluid communication with the therapy cavity. The method may furthercomprise determining flow characteristics of the system by using aprocessing element electrically coupled to the pressure sensor, thehumidity sensor, and the temperature sensor, wherein the processingelement receives property signals indicative of the pressure, humidity,and temperature.

The method may further comprise sensing an instillation pump pressureand an instillation duty cycle of the source of instillation, whereinthe instillation pump pressure and the instillation duty cycle areprovided by sensors electrically coupled to the controller. The methodmay further comprise transmitting the property signals to a controllerwithin the system for assessing the flow characteristics of the systemand using the controller to assess assessing property readingsreflective of the property signals in order to identify the flowcharacteristics of the system. The method may further comprise using thecontroller to assess the property readings and provide an alarmidentifying a blockage state condition as one of the flowcharacteristics when the instillation pump duty cycle increases, whilethe humidity remains substantially the same. The method may alsocomprise using the controller to assess the property readings andprovide an alarm identifying a fluid leak state as one of the flowcharacteristics when the instillation pump duty cycle increases and thehumidity remains substantially the same. The method may further comprisesensing pH of the fluids adjacent the tissue interface duringinstillation of liquids to the tissue interface using a pH sensormounted to the housing in fluid communication with the therapy cavity,and determining health characteristics of the tissue site by using aprocessing element mounted to the housing outside the therapy cavity andelectrically coupled to the pH sensor for receiving property signalsindicative of the pH.

Objectives, advantages, and a preferred mode of making and using theclaimed subject matter may be understood best by reference to theaccompanying drawings in conjunction with the following detaileddescription of illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram of an example embodiment of atherapy system that can provide negative-pressure and instillation inaccordance with this specification;

FIG. 2A is a graph illustrating an illustrative embodiment of pressurecontrol modes for the negative-pressure and instillation therapy systemof FIG. 1 wherein the x-axis represents time in minutes (min) and/orseconds (sec) and the y-axis represents pressure generated by a pump inTorr (mmHg) that varies with time in a continuous pressure mode and anintermittent pressure mode that may be used for applying negativepressure in the therapy system;

FIG. 2B is a graph illustrating an illustrative embodiment of anotherpressure control mode for the negative-pressure and instillation therapysystem of FIG. 1 wherein the x-axis represents time in minutes (min)and/or seconds (sec) and the y-axis represents pressure generated by apump in Torr (mmHg) that varies with time in a dynamic pressure modethat may be used for applying negative pressure in the therapy system;

FIG. 3 is a schematic block diagram showing an illustrative embodimentof a therapy method for providing negative-pressure and instillationtherapy for delivering treatment solutions to a dressing at a tissuesite;

FIG. 4 is a sectional side view of a dressing interface comprising ahousing and a wall disposed within the housing and forming a therapycavity including sensors and a component cavity including electricaldevices that may be associated with some example embodiments of thetherapy system of FIG. 1;

FIG. 5A is a perspective top view of the dressing interface of FIG. 4,FIG. 5B is a side view of the dressing interface of FIG. 4 disposed on atissue site, and FIG. 5C is an end view of the dressing interface ofFIG. 4 disposed on the tissue site;

FIG. 6A is an assembly view of the dressing interface of FIG. 4comprising components of the housing and a first example embodiment of asensor assembly including the wall, the sensors, and the electricaldevices;

FIG. 6B is a system block diagram of the sensors and electrical devicescomprising the sensor assembly of FIG. 6A;

FIGS. 7A, 7B and 7C are a top view, side view, and bottom view,respectively, of the sensor assembly of FIG. 6;

FIG. 7D is a perspective top view of the sensor assembly of the sensorassembly of FIG. 6 including one example embodiment of a pH sensor;

FIG. 8A is a perspective bottom view of the dressing interface of FIG.4, and FIG. 8B is a bottom view of the dressing interface of FIG. 4;

FIG. 9A is a top view of a first embodiment of a pH sensor that may beused with the sensor assembly of FIG. 8D, and FIG. 9B is a top view of asecond embodiment of a pH sensor that may be used with the sensorassembly of FIG. 8D;

FIG. 10 is a flow chart illustrating a method for treating a tissue siteutilizing the dressing interface of FIG. 4 for applyingnegative-pressure therapy with fluid instillation and sensing propertiesof wound exudates extracted from the tissue site;

FIG. 11 is a schematic block diagram illustrating a negative pressurecontrol algorithm utilized within the tissue treatment method of FIG. 10including the detection of dressing flow characteristics within thesystem and the assessment of sensor properties;

FIG. 12 is a block diagram of a user interface illustrating alerts andalarms associated with the dressing flow characteristics of FIG. 11;

FIG. 13A is a flow chart illustrating a wound pressure control methodconfigured to operate in the negative pressure control algorithm of FIG.11;

FIG. 13B is a flow chart illustrating a method for detecting blockagesand fluid leaks as two of the dressing flow characteristics of FIG. 11;

FIG. 13C is a flow chart illustrating a method for detecting air leaksand desiccation as two of the dressing flow characteristics of FIG. 11,and for logging and assessing the sensing properties;

FIG. 14 is a graph illustrating data associated with the detection ofblockages based on the assessment of humidity data and wound pressureover time generated by the negative pressure control algorithm of FIG.11;

FIG. 15 is a graph illustrating data associated with the detection offluid leaks based on the assessment of humidity data and wound pressuredata over time generated by the negative pressure control algorithm ofFIG. 11;

FIG. 16 is a graph illustrating data associated with the detection ofair leaks based on the assessment of humidity data, wound pressure data,and pump pressure data over time generated by the negative pressurecontrol algorithm of FIG. 11;

FIG. 17 is a graph illustrating data associated with the detection ofdesiccation conditions based on the assessment of humidity data overtime generated by the negative pressure control algorithm of FIG. 11;

FIG. 18 is a schematic block diagram illustrating a fluid instillationcontrol algorithm utilized within the tissue treatment method of FIG. 10including the detection of dressing flow characteristics within thesystem and the assessment of sensor properties and dispensed volume;

FIG. 19A is a flow chart illustrating an automated fill assist controlmethod configured to operate in the fluid instillation control algorithmof FIG. 18;

FIG. 19B is a flow chart illustrating a method for detecting blockagesand fluid leaks as two of the dressing flow characteristics of FIG. 18;and

FIG. 20 is a graph illustrating an instillation response curve includingdata associated with the relative humidity percentage of a dressing inresponse to the fluid instillation control algorithm of FIG. 18.

DESCRIPTION OF EXAMPLE EMBODIMENTS

The following description of example embodiments provides informationthat enables a person skilled in the art to make and use the subjectmatter set forth in the appended claims, but may omit certain detailsalready well-known in the art. The following detailed description is,therefore, to be taken as illustrative and not limiting.

The example embodiments may also be described herein with reference tospatial relationships between various elements or to the spatialorientation of various elements depicted in the attached drawings. Ingeneral, such relationships or orientation assume a frame of referenceconsistent with or relative to a patient in a position to receivetreatment. However, as should be recognized by those skilled in the art,this frame of reference is merely a descriptive expedient rather than astrict prescription.

The term “tissue site” in this context broadly refers to a wound,defect, or other treatment target located on or within tissue, includingbut not limited to, bone tissue, adipose tissue, muscle tissue, neuraltissue, dermal tissue, vascular tissue, connective tissue, cartilage,tendons, or ligaments. A wound may include chronic, acute, traumatic,subacute, and dehisced wounds, partial-thickness burns, ulcers (such asdiabetic, pressure, or venous insufficiency ulcers), flaps, and grafts,for example. The term “tissue site” may also refer to areas of anytissue that are not necessarily wounded or defective but are insteadareas in which it may be desirable to add or promote the growth ofadditional tissue. For example, negative pressure may be applied to atissue site to grow additional tissue that may be harvested andtransplanted.

The present technology also provides negative pressure therapy devicesand systems, and methods of treatment using such systems withantimicrobial solutions. FIG. 1 is a simplified functional block diagramof an example embodiment of a therapy system 100 that can providenegative-pressure therapy with instillation of treatment solutions inaccordance with this specification. The therapy system 100 may include anegative-pressure supply and may include or be configured to be coupledto a distribution component, such as a dressing. In general, adistribution component may refer to any complementary or ancillarycomponent configured to be fluidly coupled to a negative-pressure supplybetween a negative-pressure supply and a tissue site. A distributioncomponent is preferably detachable, and may be disposable, reusable, orrecyclable. For example, a dressing 102 is illustrative of adistribution component that may be coupled to a negative-pressure sourceand other components. The therapy system 100 may be packaged as asingle, integrated unit such as a therapy system including all of thecomponents shown in FIG. 1 that are fluidly coupled to the dressing 102.The therapy system may be, for example, a V.A.C. Ulta™ System availablefrom Kinetic Concepts, Inc. of San Antonio, Tex.

The dressing 102 may be fluidly coupled to a negative-pressure source104. A dressing may include a cover, a tissue interface, or both in someembodiments. The dressing 102, for example, may include a cover 106, adressing interface 107, and a tissue interface 108. A computer or acontroller device, such as a controller 110, may also be coupled to thenegative-pressure source 104. In some embodiments, the cover 106 may beconfigured to cover the tissue interface 108 and the tissue site and maybe adapted to seal the tissue interface and create a therapeuticenvironment proximate to a tissue site for maintaining a negativepressure at the tissue site. In some embodiments, the dressing interface107 may be configured to fluidly couple the negative-pressure source 104to the therapeutic environment of the dressing. The therapy system 100may optionally include a fluid container, such as a container 112,fluidly coupled to the dressing 102 and to the negative-pressure source104.

The therapy system 100 may also include a source of instillationsolution, such as a solution source 114. A distribution component may befluidly coupled to a fluid path between a solution source and a tissuesite in some embodiments. For example, an instillation pump 116 may becoupled to the solution source 114, as illustrated in the exampleembodiment of FIG. 1. The instillation pump 116 may also be fluidlycoupled to the negative-pressure source 104 such as, for example, by afluid conductor 119. In some embodiments, the instillation pump 116 maybe directly coupled to the negative-pressure source 104, as illustratedin FIG. 1, but may be indirectly coupled to the negative-pressure source104 through other distribution components in some embodiments. Forexample, in some embodiments, the instillation pump 116 may be fluidlycoupled to the negative-pressure source 104 through the dressing 102. Insome embodiments, the instillation pump 116 and the negative-pressuresource 104 may be fluidly coupled to two different locations on thetissue interface 108 by two different dressing interfaces. For example,the negative-pressure source 104 may be fluidly coupled to the dressinginterface 107 while the instillation pump 116 may be fluidly to thecoupled to dressing interface 107 or a second dressing interface 117. Insome other embodiments, the instillation pump 116 and thenegative-pressure source 104 may be fluidly coupled to two differenttissue interfaces by two different dressing interfaces, one dressinginterface for each tissue interface (not shown).

The therapy system 100 also may include sensors to measure operatingparameters and provide feedback signals to the controller 110 indicativeof the operating parameters properties of fluids extracted from a tissuesite. As illustrated in FIG. 1, for example, the therapy system 100 mayinclude a pressure sensor 120, an electric sensor 124, or both, coupledto the controller 110. The pressure sensor 120 may be fluidly coupled orconfigured to be fluidly coupled to a distribution component such as,for example, the negative-pressure source 104 either directly orindirectly through the container 112. The pressure sensor 120 may beconfigured to measure pressure being generated by the negative-pressuresource 104, i.e., the pump pressure (PP). The electric sensor 124 alsomay be coupled to the negative-pressure source 104 to measure the pumppressure (PP). In some example embodiments, the electric sensor 124 maybe fluidly coupled proximate the output of the output of thenegative-pressure source 104 to directly measure the pump pressure (PP).In other example embodiments, the electric sensor 124 may beelectrically coupled to the negative-pressure source 104 to measure thechanges in the current in order to determine the pump pressure (PP).

Distribution components may be fluidly coupled to each other to providea distribution system for transferring fluids (i.e., liquid and/or gas).For example, a distribution system may include various combinations offluid conductors and fittings to facilitate fluid coupling. A fluidconductor generally includes any structure with one or more luminaadapted to convey a fluid between two ends, such as a tube, pipe, hose,or conduit. Typically, a fluid conductor is an elongated, cylindricalstructure with some flexibility, but the geometry and rigidity may vary.Some fluid conductors may be molded into or otherwise integrallycombined with other components. A fitting can be used to mechanicallyand fluidly couple components to each other. For example, a fitting maycomprise a projection and an aperture. The projection may be configuredto be inserted into a fluid conductor so that the aperture aligns with alumen of the fluid conductor. A valve is a type of fitting that can beused to control fluid flow. For example, a check valve can be used tosubstantially prevent return flow. A port is another example of afitting. A port may also have a projection, which may be threaded,flared, tapered, barbed, or otherwise configured to provide a fluid sealwhen coupled to a component.

In some embodiments, distribution components may also be coupled byvirtue of physical proximity, being integral to a single structure, orbeing formed from the same piece of material. Coupling may also includemechanical, thermal, electrical, or chemical coupling (such as achemical bond) in some contexts. For example, a tube may mechanicallyand fluidly couple the dressing 102 to the container 112 in someembodiments. In general, components of the therapy system 100 may becoupled directly or indirectly. For example, the negative-pressuresource 104 may be directly coupled to the controller 110 and may beindirectly coupled to the dressing interface 107 through the container112 by conduit 126 and conduit 130. The pressure sensor 120 may befluidly coupled to the dressing 102 directly (not shown) or indirectlyby conduit 121 and conduit 122. Additionally, the instillation pump 116may be coupled indirectly to the dressing interface 107 through thesolution source 114 and the instillation regulator 115 by fluidconductors 132, 134 and 138. Alternatively, the instillation pump 116may be coupled indirectly to the second dressing interface 117 throughthe solution source 114 and the instillation regulator 115 by fluidconductors 132, 134 and 139.

The fluid mechanics of using a negative-pressure source to reducepressure in another component or location, such as within a sealedtherapeutic environment, can be mathematically complex. However, thebasic principles of fluid mechanics applicable to negative-pressuretherapy and instillation are generally well-known to those skilled inthe art, and the process of reducing pressure may be describedillustratively herein as “delivering,” “distributing,” or “generating”negative pressure, for example.

In general, exudates and other fluids flow toward lower pressure along afluid path. Thus, the term “downstream” typically implies something in afluid path relatively closer to a source of negative pressure or furtheraway from a source of positive pressure. Conversely, the term “upstream”implies something relatively further away from a source of negativepressure or closer to a source of positive pressure. Similarly, it maybe convenient to describe certain features in terms of fluid “inlet” or“outlet” in such a frame of reference. This orientation is generallypresumed for purposes of describing various features and componentsherein. However, the fluid path may also be reversed in someapplications (such as by substituting a positive-pressure source for anegative-pressure source) and this descriptive convention should not beconstrued as a limiting convention.

“Negative pressure” generally refers to a pressure less than a localambient pressure, such as the ambient pressure in a local environmentexternal to a sealed therapeutic environment provided by the dressing102. In many cases, the local ambient pressure may also be theatmospheric pressure at which a tissue site is located. Alternatively,the pressure may be less than a hydrostatic pressure associated withtissue at the tissue site. Unless otherwise indicated, values ofpressure stated herein are gauge pressures. Similarly, references toincreases in negative pressure typically refer to a decrease in absolutepressure, while decreases in negative pressure typically refer to anincrease in absolute pressure. While the amount and nature of negativepressure applied to a tissue site may vary according to therapeuticrequirements, the pressure is generally a low vacuum, also commonlyreferred to as a rough vacuum, between −5 mm Hg (−667 Pa) and −500 mm Hg(−66.7 kPa). Common therapeutic ranges are between −75 mm Hg (−9.9 kPa)and −300 mm Hg (−39.9 kPa).

A negative-pressure supply, such as the negative-pressure source 104,may be a reservoir of air at a negative pressure, or may be a manual orelectrically-powered device that can reduce the pressure in a sealedvolume, such as a vacuum pump, a suction pump, a wall suction portavailable at many healthcare facilities, or a micro-pump, for example. Anegative-pressure supply may be housed within or used in conjunctionwith other components, such as sensors, processing units, alarmindicators, memory, databases, software, display devices, or userinterfaces that further facilitate therapy. For example, in someembodiments, the negative-pressure source 104 may be combined with thecontroller 110 and other components into a therapy unit. Anegative-pressure supply may also have one or more supply portsconfigured to facilitate coupling and de-coupling the negative-pressuresupply to one or more distribution components.

The tissue interface 108 can be generally adapted to contact a tissuesite. The tissue interface 108 may be partially or fully in contact withthe tissue site. If the tissue site is a wound, for example, the tissueinterface 108 may partially or completely fill the wound or may beplaced over the wound. The tissue interface 108 may take many forms, andmay have many sizes, shapes, or thicknesses depending on a variety offactors, such as the type of treatment being implemented or the natureand size of a tissue site. For example, the size and shape of the tissueinterface 108 may be adapted to the contours of deep and irregularshaped tissue sites. Moreover, any or all of the surfaces of the tissueinterface 108 may have projections or an uneven, course, or jaggedprofile that can induce strains and stresses on a tissue site, which canpromote granulation at the tissue site.

In some embodiments, the tissue interface 108 may be a manifold such asmanifold 408 shown in FIG. 4. A “manifold” in this context generallyincludes any substance or structure providing a plurality of pathwaysadapted to collect or distribute fluid across a tissue site underpressure. For example, a manifold may be adapted to receive negativepressure from a source and distribute negative pressure through multipleapertures across a tissue site, which may have the effect of collectingfluid from across a tissue site and drawing the fluid toward the source.In some embodiments, the fluid path may be reversed, or a secondaryfluid path may be provided to facilitate delivering fluid across atissue site.

In some illustrative embodiments, the pathways of a manifold may beinterconnected to improve distribution or collection of fluids across atissue site. In some illustrative embodiments, a manifold may be aporous foam material having interconnected cells or pores. For example,cellular foam, open-cell foam, reticulated foam, porous tissuecollections, and other porous material such as gauze or felted matgenerally include pores, edges, and/or walls adapted to forminterconnected fluid channels. Liquids, gels, and other foams may alsoinclude or be cured to include apertures and fluid pathways. In someembodiments, a manifold may additionally or alternatively compriseprojections that form interconnected fluid pathways. For example, amanifold may be molded to provide surface projections that defineinterconnected fluid pathways.

The average pore size of a foam manifold may vary according to needs ofa prescribed therapy. For example, in some embodiments, the tissueinterface 108 may be a foam manifold having pore sizes in a range of400-600 microns. The tensile strength of the tissue interface 108 mayalso vary according to needs of a prescribed therapy. For example, thetensile strength of a foam may be increased for instillation of topicaltreatment solutions. In one non-limiting example, the tissue interface108 may be an open-cell, reticulated polyurethane foam such asGranuFoam® dressing or VeraFlo® foam, both available from KineticConcepts, Inc. of San Antonio, Tex.

The tissue interface 108 may be either hydrophobic or hydrophilic. In anexample in which the tissue interface 108 may be hydrophilic, the tissueinterface 108 may also wick fluid away from a tissue site, whilecontinuing to distribute negative pressure to the tissue site. Thewicking properties of the tissue interface 108 may draw fluid away froma tissue site by capillary flow or other wicking mechanisms. An exampleof a hydrophilic foam is a polyvinyl alcohol, open-cell foam such asV.A.C. WhiteFoam® dressing available from Kinetic Concepts, Inc. of SanAntonio, Tex. Other hydrophilic foams may include those made frompolyether. Other foams that may exhibit hydrophilic characteristicsinclude hydrophobic foams that have been treated or coated to providehydrophilicity.

The tissue interface 108 may further promote granulation at a tissuesite when pressure within the sealed therapeutic environment is reduced.For example, any or all of the surfaces of the tissue interface 108 mayhave an uneven, coarse, or jagged profile that can induce microstrainsand stresses at a tissue site if negative pressure is applied throughthe tissue interface 108.

In some embodiments, the tissue interface 108 may be constructed frombioresorbable materials. Suitable bioresorbable materials may include,without limitation, a polymeric blend of polylactic acid (PLA) andpolyglycolic acid (PGA). The polymeric blend may also include withoutlimitation polycarbonates, polyfumarates, and capralactones. The tissueinterface 108 may further serve as a scaffold for new cell-growth, or ascaffold material may be used in conjunction with the tissue interface108 to promote cell-growth. A scaffold is generally a substance orstructure used to enhance or promote the growth of cells or formation oftissue, such as a three-dimensional porous structure that provides atemplate for cell growth. Illustrative examples of scaffold materialsinclude calcium phosphate, collagen, PLA/PGA, coral hydroxy apatites,carbonates, or processed allograft materials.

In some embodiments, the cover 106 may provide a bacterial barrier andprotection from physical trauma. The cover 106 may also be constructedfrom a material that can reduce evaporative losses and provide a fluidseal between two components or two environments, such as between atherapeutic environment and a local external environment. The cover 106may be, for example, an elastomeric film or membrane that can provide aseal adequate to maintain a negative pressure at a tissue site for agiven negative-pressure source. The cover 106 may have a highmoisture-vapor transmission rate (MVTR) in some applications. Forexample, the MVTR may be at least 300 g/m{circumflex over ( )}2 pertwenty-four hours in some embodiments. In some example embodiments, thecover 106 may be a polymer drape, such as a polyurethane film, that ispermeable to water vapor but impermeable to liquid. Such drapestypically have a thickness in the range of 25-50 microns. For permeablematerials, the permeability generally should be low enough that adesired negative pressure may be maintained. In some embodiments, thecover may be a drape such as drape 406 shown in FIG. 4.

An attachment device may be used to attach the cover 106 to anattachment surface, such as undamaged epidermis, a gasket, or anothercover. The attachment device may take many forms. For example, anattachment device may be a medically-acceptable, pressure-sensitiveadhesive that extends about a periphery, a portion, or an entire sealingmember. In some embodiments, for example, some or all of the cover 106may be coated with an acrylic adhesive having a coating weight between25-65 grams per square meter (g.s.m.). Thicker adhesives, orcombinations of adhesives, may be applied in some embodiments to improvethe seal and reduce leaks. Other example embodiments of an attachmentdevice may include a double-sided tape, paste, hydrocolloid, hydrogel,silicone gel, or organogel.

In some embodiments, the dressing interface 107 may facilitate couplingthe negative-pressure source 104 to the dressing 102. The negativepressure provided by the negative-pressure source 104 may be deliveredthrough the conduit 130 to a negative-pressure interface, which mayinclude an elbow portion. In one illustrative embodiment, thenegative-pressure interface may be a T.R.A.C.® Pad or Sensa T.R.A.C.®Pad available from KCI of San Antonio, Tex. The negative-pressureinterface enables the negative pressure to be delivered through thecover 106 and to the tissue interface 108 and the tissue site. In thisillustrative, non-limiting embodiment, the elbow portion may extendthrough the cover 106 to the tissue interface 108, but numerousarrangements are possible.

A controller, such as the controller 110, may be a microprocessor orcomputer programmed to operate one or more components of the therapysystem 100, such as the negative-pressure source 104. In someembodiments, for example, the controller 110 may be a microcontroller,which generally comprises an integrated circuit containing a processorcore and a memory programmed to directly or indirectly control one ormore operating parameters of the therapy system 100. Operatingparameters may include the power applied to the negative-pressure source104, the pressure generated by the negative-pressure source 104, or thepressure distributed to the tissue interface 108, for example. Thecontroller 110 is also preferably configured to receive one or moreinput signals, such as a feedback signal, and programmed to modify oneor more operating parameters based on the input signals.

Sensors, such as the pressure sensor 120 or the electric sensor 124, aregenerally known in the art as any apparatus operable to detect ormeasure a physical phenomenon or property, and generally provide asignal indicative of the phenomenon or property that is detected ormeasured. For example, the pressure sensor 120 and the electric sensor124 may be configured to measure one or more operating parameters of thetherapy system 100. In some embodiments, the pressure sensor 120 may bea transducer configured to measure pressure in a pneumatic pathway andconvert the measurement to a signal indicative of the pressure measured.In some embodiments, for example, the pressure sensor 120 may be apiezoresistive strain gauge. The electric sensor 124 may optionallymeasure operating parameters of the negative-pressure source 104, suchas the voltage or current, in some embodiments. Preferably, the signalsfrom the pressure sensor 120 and the electric sensor 124 are suitable asan input signal to the controller 110, but some signal conditioning maybe appropriate in some embodiments. For example, the signal may need tobe filtered or amplified before it can be processed by the controller110. Typically, the signal is an electrical signal that is transmittedand/or received on by wire or wireless means, but may be represented inother forms, such as an optical signal.

The solution source 114 is representative of a container, canister,pouch, bag, or other storage component, which can provide a solution forinstillation therapy. Compositions of solutions may vary according to aprescribed therapy, but examples of solutions that may be suitable forsome prescriptions include hypochlorite-based solutions, silver nitrate(0.5%), sulfur-based solutions, biguanides, cationic solutions, andisotonic solutions. Examples of such other therapeutic solutions thatmay be suitable for some prescriptions include hypochlorite-basedsolutions, silver nitrate (0.5%), sulfur-based solutions, biguanides,cationic solutions, and isotonic solutions. In one illustrativeembodiment, the solution source 114 may include a storage component forthe solution and a separate cassette for holding the storage componentand delivering the solution to the tissue site 150, such as a V.A.C.VeraLink™ Cassette available from Kinetic Concepts, Inc. of San Antonio,Tex.

The container 112 may also be representative of a container, canister,pouch, or other storage component, which can be used to collect andmanage exudates and other fluids withdrawn from a tissue site. In manyenvironments, a rigid container such as, for example, a container 162,may be preferred or required for collecting, storing, and disposing offluids. In other environments, fluids may be properly disposed ofwithout rigid container storage, and a re-usable container could reducewaste and costs associated with negative-pressure therapy. In someembodiments, the container 112 may comprise a canister having acollection chamber, a first inlet fluidly coupled to the collectionchamber and a first outlet fluidly coupled to the collection chamber andadapted to receive negative pressure from a source of negative pressure.In some embodiments, a first fluid conductor may comprise a first membersuch as, for example, the conduit 130 fluidly coupled between the firstinlet and the tissue interface 108 by the negative-pressure interfacedescribed above, and a second member such as, for example, the conduit126 fluidly coupled between the first outlet and a source of negativepressure whereby the first conductor is adapted to provide negativepressure within the collection chamber to the tissue site.

The therapy system 100 may also comprise a flow regulator such as, forexample, a regulator 118 fluidly coupled to a source of ambient air toprovide a controlled or managed flow of ambient air to the sealedtherapeutic environment provided by the dressing 102 and ultimately thetissue site. In some embodiments, the regulator 118 may control the flowof ambient fluid to purge fluids and exudates from the sealedtherapeutic environment. In some embodiments, the regulator 118 may befluidly coupled by a fluid conductor or vent conduit 135 through thedressing interface 107 to the tissue interface 108. The regulator 118may be configured to fluidly couple the tissue interface 108 to a sourceof ambient air as indicated by a dashed arrow. In some embodiments, theregulator 118 may be disposed within the therapy system 100 rather thanbeing proximate to the dressing 102 so that the air flowing through theregulator 118 is less susceptible to accidental blockage during use. Insuch embodiments, the regulator 118 may be positioned proximate thecontainer 112 and/or proximate a source of ambient air where theregulator 118 is less likely to be blocked during usage.

In operation, the tissue interface 108 may be placed within, over, on,or otherwise proximate a tissue site, such as tissue site 150. The cover106 may be placed over the tissue interface 108 and sealed to anattachment surface near the tissue site 150. For example, the cover 106may be sealed to undamaged epidermis peripheral to a tissue site. Thus,the dressing 102 can provide a sealed therapeutic environment proximateto a tissue site, substantially isolated from the external environment,and the negative-pressure source 104 can reduce the pressure in thesealed therapeutic environment. Negative pressure applied across thetissue site through the tissue interface 108 in the sealed therapeuticenvironment can induce macrostrain and microstrain in the tissue site,as well as remove exudates and other fluids from the tissue site, whichcan be collected in container 112.

In one embodiment, the controller 110 may receive and process data, suchas data related to the pressure distributed to the tissue interface 108from the pressure sensor 120. The controller 110 may also control theoperation of one or more components of therapy system 100 to manage thepressure distributed to the tissue interface 108 for application to thewound at the tissue site 150, which may also be referred to as the woundpressure (WP). In one embodiment, controller 110 may include an inputfor receiving a desired target pressure (TP) set by a clinician or otheruser and may be program for processing data relating to the setting andinputting of the target pressure (TP) to be applied to the tissue site150. In one example embodiment, the target pressure (TP) may be a fixedpressure value determined by a user/caregiver as the reduced pressuretarget desired for therapy at the tissue site 150 and then provided asinput to the controller 110. The user may be a nurse or a doctor orother approved clinician who prescribes the desired negative pressure towhich the tissue site 150 should be applied. The desired negativepressure may vary from tissue site to tissue site based on the type oftissue forming the tissue site 150, the type of injury or wound (ifany), the medical condition of the patient, and the preference of theattending physician. After selecting the desired target pressure (TP),the negative-pressure source 104 is controlled to achieve the targetpressure (TP) desired for application to the tissue site 150.

Referring more specifically to FIG. 2A, a graph illustrating anillustrative embodiment of pressure control modes 200 that may be usedfor the negative-pressure and instillation therapy system of FIG. 1 isshown wherein the x-axis represents time in minutes (min) and/or seconds(sec) and the y-axis represents pressure generated by a pump in Torr(mmHg) that varies with time in a continuous pressure mode and anintermittent pressure mode that may be used for applying negativepressure in the therapy system. The target pressure (TP) may be set bythe user in a continuous pressure mode as indicated by solid line 201and dotted line 202 wherein the wound pressure (WP) is applied to thetissue site 150 until the user deactivates the negative-pressure source104. The target pressure (TP) may also be set by the user in anintermittent pressure mode as indicated by solid lines 201, 203 and 205wherein the wound pressure (WP) is cycled between the target pressure(TP) and atmospheric pressure. For example, the target pressure (TP) maybe set by the user at a value of 125 mmHg for a specified period of time(e.g., 5 min) followed by the therapy being turned off for a specifiedperiod of time (e.g., 2 min) as indicated by the gap between the solidlines 203 and 205 by venting the tissue site 150 to the atmosphere, andthen repeating the cycle by turning the therapy back on as indicated bysolid line 205 which consequently forms a square wave pattern betweenthe target pressure (TP) level and atmospheric pressure. In someembodiments, the ratio of the “on-time” to the “off-time” or the total“cycle time” may be referred to as a pump duty cycle (PD).

In some example embodiments, the decrease in the wound pressure (WP) atthe tissue site 150 from ambient pressure to the target pressure (TP) isnot instantaneous, but rather gradual depending on the type of therapyequipment and dressing being used for the particular therapy treatment.For example, the negative-pressure source 104 and the dressing 102 mayhave an initial rise time as indicated by the dashed line 207 that mayvary depending on the type of dressing and therapy equipment being used.For example, the initial rise time for one therapy system may be in therange between about 20-30 mmHg/second or, more specifically, equal toabout 25 mmHg/second, and in the range between about 5-10 mmHg/secondfor another therapy system. When the therapy system 100 is operating inthe intermittent mode, the repeating rise time as indicated by the solidline 205 may be a value substantially equal to the initial rise time asindicated by the dashed line 207.

The target pressure may also be a variable target pressure (VTP)controlled or determined by controller 110 that varies in a dynamicpressure mode. For example, the variable target pressure (VTP) may varybetween a maximum and minimum pressure value that may be set as an inputdetermined by a user as the range of negative pressures desired fortherapy at the tissue site 150. The variable target pressure (VTP) mayalso be processed and controlled by controller 110 that varies thetarget pressure (TP) according to a predetermined waveform such as, forexample, a sine waveform or a saw-tooth waveform or a triangularwaveform, that may be set as an input by a user as the predetermined ortime-varying reduced pressures desired for therapy at the tissue site150.

Referring more specifically to FIG. 2B, a graph illustrating anillustrative embodiment of another pressure control mode for thenegative-pressure and instillation therapy system of FIG. 1 is shownwherein the x-axis represents time in minutes (min) and/or seconds (sec)and the y-axis represents pressure generated by a pump in Torr (mmHg)that varies with time in a dynamic pressure mode that may be used forapplying negative pressure in the therapy system. For example, thevariable target pressure (VTP) may be a reduced pressure that providesan effective treatment by applying reduced pressure to tissue site 150in the form of a triangular waveform varying between a minimum andmaximum pressure of 50-125 mmHg with a rise time 212 set at a rate of+25 mmHg/min. and a descent time 211 set at −25 mmHg/min, respectively.In another embodiment of the therapy system 100, the variable targetpressure (VTP) may be a reduced pressure that applies reduced pressureto tissue site 150 in the form of a triangular waveform varying between25-125 mmHg with a rise time 212 set at a rate of +30 mmHg/min and adescent time 211 set at −30 mmHg/min. Again, the type of system andtissue site determines the type of reduced pressure therapy to be used.

FIG. 3 is a flow chart illustrating an illustrative embodiment of atherapy method 300 that may be used for providing negative-pressure andinstillation therapy for delivering an antimicrobial solution or othertreatment solution to a dressing at a tissue site. In one embodiment,the controller 110 receives and processes data, such as data related tofluids provided to the tissue interface. Such data may include the typeof instillation solution prescribed by a clinician, the volume of fluidor solution to be instilled to the tissue site (“fill volume”), and theamount of time needed to soak the tissue interface (“soak time”) beforeapplying a negative pressure to the tissue site. The fill volume may be,for example, between 10 and 500 mL, and the soak time may be between onesecond to 30 minutes. The controller 110 may also control the operationof one or more components of the therapy system 100 to manage the fluidsdistributed from the solution source 114 for instillation to the tissuesite 150 for application to the wound as described in more detail above.In one embodiment, fluid may be instilled to the tissue site 150 byapplying a negative pressure from the negative-pressure source 104 toreduce the pressure at the tissue site 150 to draw the instillationfluid into the dressing 102 as indicated at 302. In another embodiment,fluid may be instilled to the tissue site 150 by applying a positivepressure from the negative-pressure source 104 (not shown) or theinstillation pump 116 to force the instillation fluid from the solutionsource 114 to the tissue interface 108 as indicated at 304. In yetanother embodiment, fluid may be instilled to the tissue site 150 byelevating the solution source 114 to height sufficient to force theinstillation fluid into the tissue interface 108 by the force of gravityas indicated at 306. Thus, the therapy method 300 includes instillingfluid into the tissue interface 108 by either drawing or forcing thefluid into the tissue interface 108 as indicated at 310.

The therapy method 300 may control the fluid dynamics of applying thefluid solution to the tissue interface 108 at 312 by providing acontinuous flow of fluid at 314 or an intermittent flow of fluid forsoaking the tissue interface 108 at 316. The therapy method 300 mayinclude the application of negative pressure to the tissue interface 108to provide either the continuous flow or intermittent soaking flow offluid at 320. The application of negative pressure may be implemented toprovide a continuous pressure mode of operation at 322 as describedabove to achieve a continuous flow rate of instillation fluid throughthe tissue interface 108 or a dynamic pressure mode of operation at 324as described above to vary the flow rate of instillation fluid throughthe tissue interface 108. Alternatively, the application of negativepressure may be implemented to provide an intermittent mode of operationat 326 as described above to allow instillation fluid to soak into thetissue interface 108 as described above. In the intermittent mode, aspecific fill volume and the soak time may be provided depending, forexample, on the type of wound being treated and the type of dressing 102being utilized to treat the wound. After or during instillation of fluidinto the tissue interface 108 has been completed, the therapy method 300may begin may be utilized using any one of the three modes of operationat 330 as described above. The controller 110 may be utilized to selectany one of these three modes of operation and the duration of thenegative pressure therapy as described above before commencing anotherinstillation cycle at 340 by instilling more fluid at 310.

As discussed above, the tissue site 150 may include, without limitation,any irregularity with a tissue, such as an open wound, surgicalincision, or diseased tissue. The therapy system 100 is presented in thecontext of a tissue site that includes a wound that may extend throughthe epidermis and the dermis and may reach into the hypodermis orsubcutaneous tissue. The therapy system 100 may be used to treat a woundof any depth, as well as many different types of wounds including openwounds, incisions, or other tissue sites. The tissue site 150 may be thebodily tissue of any human, animal, or other organism, including bonetissue, adipose tissue, muscle tissue, dermal tissue, vascular tissue,connective tissue, cartilage, tendons, ligaments, or any other tissue.Treatment of the tissue site 150 may include removal of fluidsoriginating from the tissue site 150, such as exudates or ascites, orfluids instilled into the dressing to cleanse or treat the tissue site150, such as antimicrobial solutions.

As indicated above, the therapy system 100 may be packaged as a single,integrated unit such as a therapy system including all of the componentsshown in FIG. 1 that are fluidly coupled to the dressing 102. In someembodiments, an integrated therapy unit may include thenegative-pressure source 104, the controller 110, the pressure sensor120, and the container 112 which may be fluidly coupled to the dressinginterface 107. In this therapy unit, the negative-pressure source 104 isindirectly coupled to the dressing interface 107 through the container112 by conduit 126 and conduit 130, and the pressure sensor 120 isindirectly coupled to the dressing interface 107 by conduit 121 andconduit 122 as described above. In some embodiments, the negativepressure conduit 130 and the pressure sensing conduit 122 may becombined in a single fluid conductor that can be, for example, amulti-lumen tubing comprising a central primary lumen that functions asthe negative pressure conduit 130 for delivering negative pressure tothe dressing interface 107 and several peripheral auxiliary lumens thatfunction as the pressure sensing conduit 122 for sensing the pressurethat the dressing interface 107 delivers to the tissue interface 108. Inthis type of therapy unit wherein the pressure sensor 120 is removedfrom and indirectly coupled to the dressing interface 107, the negativepressure measured by the pressure sensor 120 may be different from thewound pressure (WP) actually being applied to the tissue site 150. Suchpressure differences must be approximated in order to adjust thenegative-pressure source 104 to deliver the pump pressure (PP) necessaryto provide the desired or target pressure (TP) to the tissue interface108. Moreover, such pressure differences and predictability may beexacerbated by viscous fluids such as exudates being produced by thetissue site or utilizing a single therapy device including a pressuresensor to deliver negative pressure to multiple tissue sites on a singlepatient.

What is needed is a pressure sensor that is integrated within thedressing interface 107 so that the pressure sensor is proximate thetissue interface 108 when disposed on the tissue site in order toprovide a more accurate reading of the wound pressure (WP) beingprovided within the therapy environment of the dressing 102. Theintegrated pressure sensor may be used with or without the remotepressure sensor 120 that is indirectly coupled to the dressing interface107. In some example embodiments, the dressing interface 107 maycomprise a housing having a therapy cavity that opens to the tissue sitewhen positioned thereon. The integrated pressure sensor may have asensing portion disposed within the therapy cavity along with othersensors including, for example, a temperature sensor, a humidity sensor,and a pH sensor. The sensors may be electrically coupled to thecontroller 110 outside the therapy cavity to provide data indicative ofthe pressure, temperature, humidity, and acidity properties within thetherapeutic space of the therapy cavity. The sensors may be electricallycoupled to the controller 110, for example, by wireless means. Systems,apparatuses, and methods described herein provide the advantage of moreaccurate measurements of these properties, as well as other significantadvantages described below in more detail.

As indicated above, the dressing 102 may include the cover 106, thedressing interface 107, and the tissue interface 108. Referring now toFIGS. 4, 5A, 5B, 5C, 6A, 6B, and 7, a first dressing is shown comprisinga dressing interface 400, a cover or drape 406, and a tissue interfaceor manifold 408 disposed adjacent a tissue site 410, all of which may befunctionally similar in part to the dressing interface 107, the cover106, and the tissue interface 108, respectively, as described above. Inone example embodiment, the dressing interface 400 may comprise ahousing 401 and a wall 402 disposed within the housing 401 wherein thewall 402 forms a recessed space or a therapy cavity 403 that opens tothe manifold 408 when disposed at the tissue site 410 and a componentcavity 404 opening away from the tissue site 410 of the upper portion ofthe dressing interface 400. In some embodiments, sensing portions ofvarious sensors may be disposed within the therapy cavity 403, andelectrical devices associated with the sensors may be disposed withinthe component cavity 404 and electrically coupled to the sensingportions through the wall 402. Electrical devices disposed within thecomponent cavity 404 may include components associated with some exampleembodiments of the therapy system of FIG. 1. Although the dressinginterface 400 and the therapy cavity 403 are functionally similar to thedressing interface 107 as described above, the dressing interface 400further comprises the wall 402, the sensors, and the associatedelectrical devices described below in more detail. In some embodiments,the housing 401 may further comprise a neck portion or neck 407 fluidlycoupled to a conduit 405. In some embodiments, the housing 401 mayfurther comprise a flange portion or flange 409 having flow channels(see FIG. 8) configured to be fluidly coupled to the therapy cavity 403when disposed on the manifold 408.

In some example embodiments, the neck 407 of the housing 401 may includeportions of both the therapy cavity 403 and the component cavity 404.That portion of the neck 407 extending into the therapy cavity 403 isfluidly coupled to the conduit 405, while the portion extending into thecomponent cavity 404 may contain some of the electrical devices. In someexample embodiments, the conduit 405 may comprise a primary lumen 430and auxiliary lumens 435 fluidly coupled by the neck 407 of the housing401 to the therapy cavity 403. The primary lumen 430 is similar to thenegative pressure conduit 130 that may be coupled indirectly to thenegative-pressure source 104. The auxiliary lumens 435 are collectivelysimilar to the vent conduit 135 that may be fluidly coupled to theregulator 118 for purging fluids from the therapy cavity 403.

In some embodiments, the component cavity 404 containing the electricaldevices may be open to the ambient environment such that the electricaldevices are exposed to the ambient environment. In other exampleembodiments, the component cavity 404 may be closed by a cover such as,for example, a cap 411 to protect the electrical devices. In still otherembodiments, the component cavity 404 covered by the cap 411 may stillbe vented to the ambient environment to provide cooling to theelectrical devices and a source of ambient pressure for a pressuresensor disposed in the therapy cavity 403 as described in more detailbelow. The first dressing may further comprise a drape ring 413 coveringthe circumference of the flange 409 and the adjacent portion of thedrape 406 to seal the therapy cavity 403 of the housing 401 over themanifold 408 and the tissue site 410. In some embodiments, the drapering 413 may comprise a polyurethane film including and an attachmentdevice such as, for example, an acrylic, polyurethane gel, silicone, orhybrid combination of the foregoing adhesives (not shown) to attach thedrape ring 413 to the flange 409 and the drape 406. The attachmentdevice of drape ring 413 may be a single element of silicon orhydrocolloid with the adhesive on each side that functions as a gasketbetween the drape 406 and the flange 409. In some embodiments, the drapering 413 may be similar to the cover 106 and/or the attachment devicedescribed above in more detail.

In some embodiments, a pressure sensor 416, a temperature and humiditysensor 418, and a pH sensor 420 (collectively referred to below as “thesensors”) may be disposed in the housing 401 with each one having asensing portion extending into the therapy cavity 403 of the housing 401and associated electronics disposed within the component cavity 404. Thehousing 401 may include other types of sensors, or combinations of theforegoing sensors, such as, for example, oxygen sensors. In some exampleembodiments, the sensors may be coupled to or mounted on the wall 402and electrically coupled to electrical components and circuits disposedwithin the component cavity 404 by electrical conductors extendingthrough the wall 402. In some preferred embodiments, the electricalconductors extend through pathways in the wall 402 while keeping thetherapy cavity 403 electrically and pneumatically isolated from thecomponent cavity 404. For example, the wall 402 may comprise a circuitboard 432 on which the electrical circuits and/or components may beprinted or mounted. In some other examples, the circuit board 432 may bethe wall 402 that covers an opening between the therapy cavity 403 andthe component cavity 404, and pneumatically seals the therapy cavity 403from the component cavity 404 when seated over the opening.

In some embodiments, the electrical circuits and/or componentsassociated with the sensors that are mounted on the circuit board 432within the component cavity 404 may be electrically coupled to thecontroller 110 to interface with the rest of the therapy system 100 asdescribed above. In some embodiments, for example, the electricalcircuits and/or components may be electrically coupled to the controller110 by a conductor that may be a component of the conduit 405. In someother preferred embodiments, a communications module 422 may be disposedin the component cavity 404 of the housing 401 and mounted on thecircuit board 432 within the component cavity 404. Using a wirelesscommunications module 422 has the advantage of eliminating an electricalconductor between the dressing interface 400 and the integrated portionof the therapy system 100 that may become entangled with the conduit 405when in use during therapy treatments. For example, the electricalcircuits and/or components associated with the sensors along with theterminal portion of the sensors may be electrically coupled to thecontroller 110 by wireless means such as an integrated deviceimplementing Bluetooth® Low Energy wireless technology. Morespecifically, the communications module 422 may be a Bluetooth® LowEnergy system-on-chip that includes a microprocessor (an example of themicroprocessors referred to hereinafter) such as the nRF51822 chipavailable from Nordic Semiconductor. The wireless communications module422 may be implemented with other wireless technologies suitable for usein the medical environment.

In some embodiments, a voltage regulator 423 for signal conditioning anda power source 424 may be disposed within the component cavity 404 ofthe housing 401, mounted on the circuit board 432. The power supply 424may be secured to the circuit board 432 by a bracket 426. The powersource 424 may be, for example, a battery that may be a coin batteryhaving a low-profile that provides a 3-volt source for thecommunications module 422 and the other electronic components within thecomponent cavity 404 associated with the sensors. In some exampleembodiments, the sensors, the electrical circuits and/or componentsassociated with the sensors, the wall 402 and/or the circuit board 432,the communications module 422, and the power source 424 may beintegrated into a single package and referred to hereinafter as a sensorassembly 425 as shown in FIG. 6B. In some preferred embodiments, thewall 402 of the sensor assembly 425 may be the circuit board 432 itselfas described above that provides a seal between tissue site 410 and theatmosphere when positioned over the opening between the therapy cavity403 and the component cavity 404 of the housing 401 and functions as thewall 402 within the housing 401 that forms the therapy cavity 403.

Referring now to FIGS. 8A and 8B, a perspective view and a bottom view,respectively, of a bottom surface of the flange 409 facing the manifold408 is shown. In some embodiments, the bottom surface may comprisefeatures or channels to direct the flow of liquids and/or exudates awayfrom the sensors out of the therapy cavity 403 into the primary lumen430 when negative pressure is being applied to the therapy cavity 403.In some embodiments, these channels may be molded into the bottomsurface of the flange 409 to form a plurality of serrated guide channels437, perimeter collection channels 438, and intermediate collectionchannels 439. The serrated guide channels 437 may be positioned andoriented in groups on bottom surface to directly capture and channel atleast half of the liquids being drawn into the therapy cavity 403 withthe groups of serrated guide channels 437, and indirectly channel amajor portion of the balance of the liquids being drawn into the therapycavity 403 between the groups of serrated guide channels 437. Inaddition, perimeter collection channels 438 and intermediate collectionchannels 439 redirect the flow of liquids that are being drawn inbetween the groups of radially-oriented serrated guide channels 437 intothe guide channels 437. An example of this redirected flow isillustrated by bolded flow arrows 436. In some example embodiments, aportion of the housing 401 within the therapy cavity 403 may comprise asecond set of serrated guide channels 427 spaced apart andradially-oriented to funnel liquids being drawn into the therapy cavity403 from the flange 409 into the primary lumen 430. In other exampleembodiments of the bottom surface of the flange 409 and that portion ofthe housing 401 within the therapy cavity 403, the channels may bearranged in different patterns.

As indicated above, the sensor assembly 425 may comprise a pressuresensor 416, a humidity sensor 418, a temperature sensor as a componentof either the pressure sensor 416 or the humidity sensor 418, and a pHsensor 420. Each of the sensors may comprise a sensing portion extendinginto the therapy cavity 403 of the housing 401 and a terminal portionelectrically coupled to the electrical circuits and/or components withinthe component cavity 404. Referring more specifically to FIGS. 4, 6A,6B, and 7A-7D, the housing 401 may comprise a sensor bracket 441 thatmay be a molded portion of the housing 401 within the therapy cavity 403in some embodiments. The sensor bracket 441 may be structured to houseand secure the pressure sensor 416 on the circuit board 432 within thetherapy cavity 403 of the sensor assembly 425 that provides a sealbetween tissue site 410 and the atmosphere as described above. In someembodiments, the pressure sensor 416 may be a differential gaugecomprising a sensing portion 442 and a terminal portion or vent 443. Thevent 443 of the pressure sensor 416 may be fluidly coupled through thecircuit board 432 to the component cavity 404 and the atmosphere by avent hole 444 extending through the circuit board 432. Because thecomponent cavity 404 is vented to the ambient environment, the vent 443of the pressure sensor 416 is able to measure the wound pressure (WP)with reference to the ambient pressure. The sensing portion 442 of thepressure sensor 416 may be positioned in close proximity to the manifold408 to optimize fluid coupling and accurately measure the wound pressure(WP) at the tissue site 410. In some embodiments, the pressure sensor416 may be a piezo-resistive pressure sensor having a pressure sensingelement covered by a dielectric gel such as, for example, a Model 1620pressure sensor available from TE Connectivity. The dielectric gelprovides electrical and fluid isolation from the blood and woundexudates in order to protect the sensing element from corrosion or otherdegradation. This allows the pressure sensor 416 to measure the woundpressure (WP) directly within the therapy cavity 403 of the housing 401proximate to the manifold 408 as opposed to measuring the wound pressure(WP) from a remote location. In some embodiments, the pressure sensor416 may be a gauge that measures the absolute pressure that does notneed to be vented.

In some embodiments, the pressure sensor 416 also may comprise atemperature sensor for measuring the temperature at the tissue site 410.In other embodiments, the humidity sensor 418 may comprise a temperaturesensor for measuring the temperature at the tissue site 410. The sensorbracket 441 also may be structured to support the humidity sensor 418 onthe circuit board 432 of the sensor assembly 425. In some embodiments,the humidity sensor 418 may comprise a sensing portion that iselectrically coupled through the circuit board 432 to a microprocessormounted on the other side of the circuit board 432 within the componentcavity 404. The sensing portion of the humidity sensor 418 may befluidly coupled to the space within the therapy cavity 403 that includesa fluid pathway 445 extending from the therapy cavity 403 into theprimary lumen 430 of the conduit 405 as indicated by the bold arrow tosense both the humidity and the temperature. The sensing portion of thehumidity sensor 418 may be positioned within the fluid pathway 445 tolimit direct contact with bodily fluids being drawn into the primarylumen 430 from the tissue site 410. In some embodiments, the spacewithin the therapy cavity 403 adjacent the sensing portion of thehumidity sensor 418 may be purged by venting that space through theauxiliary lumens 435 as described in more detail below. As indicatedabove, the humidity sensor 418 may further comprise a temperature sensor(not shown) as the location within the fluid pathway 445 is well-suitedto achieve accurate readings of the temperature of the fluids. In someembodiments, the humidity sensor 418 that comprises a temperature sensormay be a single integrated device such as, for example, Model HTU28humidity sensor also available from TE Connectivity.

Referring now to FIGS. 9A and 9B, the pH sensor 420 may comprise asensing portion disposed within the therapy cavity 403 that iselectrically coupled through the circuit board 432 to a front-endamplifier 421 mounted on the other side of the circuit board 432 withinthe component cavity 404. The front-end amplifier 421 comprises analogsignal conditioning circuitry that includes sensitive analog amplifierssuch as, for example, operational amplifiers, filters, andapplication-specific integrated circuits. The front-end amplifier 421measures minute voltage potential changes provided by the sensingportions to provide an output signal indicative of the pH of the fluids.The sensing portion of the pH sensor 420 may be fluidly coupled to thespace within the therapy cavity 403 by being positioned in the fluidpathway 445 that extends into the primary lumen 430 as described aboveto sense the pH changes. The sensing portion of the pH sensor 420 may beformed and positioned within the fluid pathway 445 so that the sensingportion directly contacts the wound fluid without contacting the wounditself so that the sensing portion of the pH sensor 420 does notinterfere with the wound healing process. In some embodiments, the spacewithin the therapy cavity 403 adjacent the sensing portion of the pHsensor 420 also may be purged by venting that space through theauxiliary lumens 435 as described in more detail below. In someembodiments, the pH sensor 420 may be, for example, pH sensor 450 shownin FIG. 9A that comprises a pair of printed medical electrodes includinga working electrode 451 and a reference electrode 452. In someembodiments, the working electrode 451 may have a node beingsubstantially circular in shape at one end and having a terminal portionat the other end, and the reference electrode 452 may have a node beingsubstantially semicircular in shape and disposed around the node of theworking electrode 451.

In some example embodiments, the working electrode 451 may comprise amaterial selected from a group including graphene oxide ink, conductivecarbon, carbon nanotube inks, silver, nano-silver, silver chloride ink,gold, nano-gold, gold-based ink, metal oxides, conductive polymers, or acombination thereof. This working electrode 451 further comprise acoating or film applied over the material wherein such coating or filmmay be selected from a group including metal oxides such as, forexample, tungsten, platinum, iridium, ruthenium, and antimony oxides, ora group of conductive polymers such as polyaniline and others so thatthe conductivity of the working electrode 451 changes based on changesin hydrogen ion concentration of the fluids being measured or sampled.In some example embodiments, the reference electrode 452 may comprise amaterial selected from a group including silver, nano-silver, silverchloride ink, or a combination thereof. The pH sensor 450 may furthercomprise a coating 453 covering the electrodes that insulates andisolates the working electrode 451 from the reference electrode 452 andthe wound fluid, except for an electrical coupling space 454 between thenodes of the working electrode 451 and the reference electrode 452. Thecoating 453 does not cover the terminal portions of the workingelectrode 451 and the reference electrode 452 to form terminals 455 and456, respectively, adapted to be electrically coupled to the front-endamplifier 421.

In some example embodiments, the terminal portion of the workingelectrode 451 and the reference electrode 452 may extend through thecircuit board 432 and electrically coupled to the front-end amplifier421 of the pH sensor 450. As indicated above, the front-end amplifier421 of the pH sensor 450 measures minute potential changes between theworking electrode 451 and the reference electrode 452 that result from achange in hydrogen ion concentration of the wound fluid as the pH of thewound fluid changes. The front-end amplifier 421 may be, for example, anextremely accurate voltmeter that measures the voltage potential betweenthe working electrode 451 and the reference electrode 452. The front-endamplifier 421 may be for example a high impedance analog front-end (AFE)device such as the LMP7721 and LMP91200 chips that are available frommanufacturers such as Texas Instruments or the AD7793 and AD8603 chipsthat are available from manufacturers such as Analog Devices.

In some other embodiments, the pH sensor 420 may include a thirdelectrode such as, for example, pH sensor 460 shown in FIG. 9B thatcomprises a third electrode or a counter electrode 462 in addition tothe working electrode 451 and the reference electrode 452 of the pHsensor 450. The counter electrode 462 also comprises a node partiallysurrounding the node of the working electrode 451 and a terminal 466adapted to be electrically coupled to the front-end amplifier 421.Otherwise, the pH sensor 460 is substantially similar to the pH sensor450 described above as indicated by the reference numerals. The counterelectrode 462 is also separated from the working electrode 451 and isalso insulated from the wound fluid and the other electrodes by thecoating 453 except in the electrical conductive space 454. The counterelectrode 462 may be used in connection with the working electrode 451and the reference electrode 452 for the purpose of error correction ofthe voltages being measured. For example, the counter electrode 462 maypossess the same voltage potential as the potential of the workingelectrode 451 except with an opposite sign so that any electrochemicalprocess affecting the working electrode 451 will be accompanied by anopposite electrochemical process on the counter electrode 462. Althoughvoltage measurements are still being taken between the working electrode451 and the reference electrode 452 by the analog front-end device ofthe pH sensor 460, the counter electrode 462 may be used for such errorcorrection and may also be used for current readings associated with thevoltage measurements. Custom printed electrodes assembled in conjunctionwith a front-end amplifier may be used to partially comprise pH sensorssuch as the pH sensor 450 and the pH sensor 460 may be available fromseveral companies such as, for example, GSI Technologies, Inc. andDropsens.

As described above, the sensing portions of the sensors may all bedisposed within the therapy cavity 403 and electrically coupled throughthe circuit board 432 to the front-end amplifier 421 and thecommunications module 422 mounted on the other side of the circuit board432 within the component cavity 404. In some embodiments, sensorassembly 425 may comprise a processing element that may include thecommunications module 422 which may include the microprocessor, and/orthe wireless communications chip described above. The processing elementmay further include the front-end amplifier 421 and any other componentsthat are disposed within the component cavity 404. The processingelement may be electrically coupled to the sensing portions of thesensors for receiving property signals from the sensing portions thatare indicative of the pressure, humidity, temperature, and the pH of thefluid at the tissue site in order to determine the flow characteristicsof the system and the progression of wound healing as described in moredetail below.

The systems, apparatuses, and methods described herein may provide othersignificant advantages. For example, some therapy systems are a closedsystem wherein the pneumatic pathway is not vented to ambient air, butrather controlled by varying the supply pressure or the pump pressure(PP) to achieve the desired target pressure (TP) in a continuouspressure mode, an intermittent pressure mode, or a variable targetpressure mode as described above in more detail with reference to FIGS.2A and 2B. In some embodiments of the closed system, the wound pressure(WP) being measured in the dressing interface 107 may not drop inresponse to a decrease in the supply pressure or the pump pressure (PP)as a result of a blockage within the dressing interface 107 or otherportions of the pneumatic pathway. In some embodiments of the closedsystem, the supply pressure or the pump pressure (PP) may not provideairflow to the tissue interface 108 frequently enough that may result inthe creation of a significant head pressure or blockages within thedressing interface 107 that also would interfere with sensormeasurements being taken by the dressing interface 400 as describedabove. The head pressure in some embodiments may be defined as adifference in pressure (DP) between a negative pressure set by a user orcaregiver for treatment, i.e., the target pressure (TP), and thenegative pressure provided by a negative pressure source that isnecessary to offset the pressure drop inherent in the fluid conductors,i.e., the supply pressure or the pump pressure (PP), in order to achieveor reach the target pressure (TP). For example, the head pressure that anegative pressure source needs to overcome may be as much as 75 mmHg.Problems may occur in such closed systems when a blockage occurs in thepneumatic pathway of the fluid conductors that causes the negativepressure source to increase to a value above the normal supply pressureor the pump pressure (PP) as a result of the blockage. For example, ifthe blockage suddenly clears, the instantaneous change in the pressurebeing supplied may cause harm to the tissue site.

Some therapy systems have attempted to compensate for head pressure byintroducing a supply of ambient air flow into the therapeuticenvironment, e.g., the therapy cavity 403, by providing a vent with afilter on the housing 401 of the dressing interface 400 to provideambient air flow into the therapeutic environment as a controlled leak.However, in some embodiments, the filter may be blocked when theinterface dressing is applied to the tissue site or when asked at leastblocked during use. Locating the filter in such a location may also beproblematic because it is more likely to be contaminated or compromisedby other chemicals and agents associated with treatment utilizinginstillation fluids that could adversely affect the performance of thefilter and the vent itself.

The embodiments of the therapy systems described herein overcome theproblems associated with having a large head pressure in a closedpneumatic environment, and the problems associated with using a ventdisposed on or adjacent the dressing interface. More specifically, theembodiments of the therapy systems described above comprise a pressuresensor, such as the pressure sensor 416, disposed within the pneumaticenvironment, i.e., in situ, that independently measures the woundpressure (WP) within the therapy cavity 403 of the housing 401 asdescribed above rather than doing so remotely. Consequently, thepressure sensor 416 is able to instantaneously identify dangerously highhead pressures and/or blockages within the therapy cavity 403 adjacentthe manifold 408. Because the auxiliary lumens 435 are not being usedfor pressure sensing, the auxiliary lumens 435 may be fluidly coupled toa fluid regulator such as, for example, the regulator 118 in FIG. 1,that may remotely vent the therapeutic environment within the therapycavity 403 to the ambient environment or fluidly couple the therapeuticenvironment to a source of positive pressure. The regulator 118 may thenbe used to provide ambient air or positive pressure to the therapeuticenvironment in a controlled fashion to “purge” the therapeuticenvironment within both the therapy cavity 403 and the primary lumen 430to resolve the problems identified above regarding head pressures andblockages, and to facilitate the continuation of temperature, humidity,and pH measurements as described above.

Using a regulator to purge the therapeutic environment is especiallyimportant in therapy systems such as those disclosed in FIGS. 1 and 3that include both negative pressure therapy and instillation therapy fordelivering therapeutic liquids to a tissue site. For example, in oneembodiment, fluid may be instilled to the tissue site 150 by applying anegative pressure from the negative-pressure source 104 to reduce thepressure at the tissue site 150 to draw the instillation liquid into thedressing 102 as indicated at 302. In another embodiment, liquid may beinstilled to the tissue site 150 by applying a positive pressure fromthe negative-pressure source 104 (not shown) or the instillation pump116 to force the instillation liquid from the solution source 114 to thetissue interface 108 as indicated at 304. Such embodiments may not besufficient to remove all the instillation liquids from the therapeuticenvironment or may not be sufficient to remove the instillation liquidsquickly enough from the therapeutic environment to facilitate thecontinuation of accurate temperature, humidity, and pH measurements.Thus, the regulator 118 may be used to provide ambient air or positivepressure to the therapeutic environment to more completely or quicklypurge the therapeutic environment to obtain the desired measurements asdescribed above.

In embodiments of therapy systems that include an air flow regulatorcomprising a valve such as the solenoid valve described above, the valveprovides controlled airflow venting or positive pressure to the therapycavity 403 as opposed to a constant airflow provided by a closed systemor an open system including a filter in response to the wound pressure(WP) being sensed by the pressure sensor 416. The controller 110 may beprogrammed to periodically open the solenoid valve as described aboveallowing ambient air to flow into the therapy cavity 403, or applying apositive pressure into the therapy cavity 403, at a predetermined flowrate and/or for a predetermined duration of time to purge the pneumaticsystem including the therapy cavity 403 and the primary lumen 430 ofbodily liquids and exudates so that the humidity sensor 418 and the pHsensor 420 provide more accurate readings and in a timely fashion. Thisfeature allows the controller to activate the solenoid valve in apredetermined fashion to purge blockages and excess liquids that maydevelop in the fluid pathways or the therapy cavity 403 duringoperation. In some embodiments, the controller may be programmed to openthe solenoid valve for a fixed period of time at predetermined intervalssuch as, for example, for five seconds every four minutes to mitigatethe formation of any blockages.

In some other embodiments, the controller may be programmed to open thesolenoid valve in response to a stimulus within the pneumatic systemrather than, or additionally, being programmed to function on apredetermined therapy schedule. For example, if the pressure sensor isnot detecting pressure decay in the canister, this may be indicative ofa column of fluid forming in the fluid pathway or the presence of ablockage in the fluid pathway. Likewise, the controller may beprogrammed to recognize that an expected drop in canister pressure as aresult of the valve opening may be an indication that the fluid pathwayis open. The controller may be programmed to conduct such testsautomatically and routinely during therapy so that the patient orcaregiver can be forewarned of an impending blockage. The controller mayalso be programmed to detect a relation between the extent of thedeviation in canister pressure resulting from the opening of the valveand the volume of fluid with in the fluid pathway. For example, if thepressure change within the canister is significant when measured, thiscould be an indication that there is a significant volume of fluidwithin the fluid pathway. However, if the pressure change within thecanister is not significant, this could be an indication that the plenumvolume was larger.

The systems, apparatuses, and methods described herein may provide othersignificant advantages over dressing interfaces currently available. Forexample, a patient may require two dressing interfaces for two tissuesites, but wish to use only a single therapy device to provide negativepressure to and collect fluids from the multiple dressing interfaces tominimize the cost of therapy. In some therapy systems currentlyavailable, the two dressing interfaces would be fluidly coupled to thesingle therapy device by a Y-connector. The problem with thisarrangement is that the Y-connector embodiment would not permit thepressure sensor in the therapy device to measure the wound pressure inboth dressing interfaces independently from one another. A significantadvantage of using a dressing interface including in situ sensors, e.g.,the dressing interface 400 including the sensor assembly 425 and thepressure sensor 416, is that multiple dressings may be fluidly coupledto the therapy unit of a therapy system and independently providepressure data to the therapy unit regarding the associated dressinginterface. Each dressing interface 400 including in situ sensors that isfluidly coupled to the therapy unit for providing negative pressure tothe tissue interface 108 and collecting fluids from the tissue interface108 has the additional advantage of being able to collect and monitorother information at the tissue site including, for example, humiditydata, temperature data, and the pH data being provided by the sensorassembly 425 in addition to the pressure data and other data that mightbe available from other sensors in the sensor assembly 425.

Another advantage of using the dressing interface 400 that includes apressure sensor in situ such as, for example, the pressure sensor 416,is that the pressure sensor 416 can more accurately monitor the woundpressure (WP) at the tissue site and identify blockages and fluid leaksthat may occur within the therapeutic space or other distributioncomponents of the system as described in more detail above. Anotheradvantage of using the dressing interface 400 that includes a pressuresensor in situ is that one of the auxiliary lumens 435 are freed up tovent or actively purge the sensing portions of the sensors within thetherapeutic cavity 403 so that meaningful data regarding the sensingproperties can be obtained on a timely basis for providing the therapyand detecting the flow characteristics of the system and the status ofwound healing. Yet another advantage of using a dressing interfaceincluding in situ sensors, e.g., the dressing interface 400, is that thesensor assembly 425 provides additional data including pressure,temperature, humidity, and pH of the fluids being drawn from the tissuesite that facilitates improved control algorithms for detecting flowcharacteristics within the system and profiling the status of woundhealing. Such improvements further assist the caregiver with additionalinformation provided by the therapy unit of the therapy system tooptimize the wound therapy being provided and the overall healingprogression of the tissue site when combined with appropriate controllogic.

As indicated above, the processing element of the sensor assembly 425may receive property signals indicative of the pressure, the humidity,the temperature, and the pH within the therapy cavity 403 that may betransmitted to the controller 110 of the system for applying therapy tothe tissue site and detecting the flow characteristics of the system andthe status of wound healing at the tissue site. In some embodiments, theflow characteristics may include the detection of blockages, fluidlyleaks, air leaks, and desiccation conditions associated with thedressing interface and the system. The property signals associated withthe fluids at a specific time may be processed and logged by thecontroller 110 and assessed with previous property signal measurements.The controller 110 may also be programmed with a negative pressurecontrol algorithm that assesses the logged property signals to assessthe status of wound healing and with that assessment adjust the pumppressure (PP) and/or the pump duty cycle (PD) if necessary to maintainthe wound pressure (WP) proximate the desired target pressure (TP).

Referring to FIG. 10, a flowchart is shown that illustrates a method fortreating a tissue site in some embodiments of therapy systems including,for example, the therapy system 100. More specifically, such method mayutilize a dressing interface or sensing pad such as, for example, thedressing interface 400 of FIG. 4, for applying negative-pressure therapywith fluid instillation therapy and sensing properties of wound exudatesextracted from a tissue site as shown at 600. A tissue interface such asthe tissue interface 108 may be placed within, over, on, or otherwiseproximate a tissue site at 601. A cover such as the cover 106 may beplaced over the tissue interface 108 and sealed to an attachment surfacenear the tissue site 150. For example, the cover 106 may be sealed toundamaged epidermis peripheral to a tissue site. Thus, the dressing 102provides a sealed therapeutic environment proximate to a tissue site,substantially isolated from the external environment, while thenegative-pressure source 104 reduces the pressure within the sealedtherapeutic environment and the instillation pump 116 provides fluids tothe sealed therapeutic environment as described above. In someembodiments, the method may further comprise applying the sensing pad ordressing interface to the tissue interface at 602. More specifically,applying the sensing pad may include positioning the housing on thedressing interface so that the aperture of the housing is in fluidcommunication with the tissue interface. The dressing interface maycomprise a wall disposed within the housing to form a therapy cavitywithin the housing and a component cavity fluidly sealed from thetherapy cavity, wherein the therapy cavity opens to the aperture asdescribed above. Such dressing interface may further comprise anegative-pressure port fluidly coupled to the therapy cavity and adaptedto be fluidly coupled to a negative-pressure source as described above.The dressing interface may further comprise a processing elementdisposed in the component cavity or outside the therapy cavity, similarto the processing element described above.

Still referring to 602, the method may further comprise connecting thesensing pad to a wound therapy device such as, for example, the therapysystem 100. Connecting the sensing pad may include coupling the therapycavity of the sensing pad to a negative-pressure source and to a vent asdescribed above, and electrically coupling the processing element to acontroller of the therapy system such as, for example, the controller110. The sensing pad or the dressing interface may further comprise a pHsensor, a temperature sensor, a humidity sensor, and a pressure sensor,each having a sensing portion disposed within the therapy cavity andeach electrically coupled to the processing element through the wall asdescribed above.

Referring now to 603, the method may further comprise initializingtherapy settings for both the negative pressure therapy and the fluidinstillation therapy to be provided for treatment. The therapy settingsmay include, for example, the initial settings for the sensor readingsof the pH sensor, the temperature sensor, the humidity sensor, and thepressure sensor that may be stored on the controller 110. The therapysettings for the negative pressure therapy phase may also include, forexample, any initial values associated with the pump pressure (PP), thepump duty cycle (PD), or the desired target pressure (TP) of thenegative-pressure source 104. The therapy settings for the fluidinstillation therapy phase may further include any initial valuesassociated with the fill volume and the soak time, as well as aninstillation pump pressure (IP), an instillation duty cycle (ID), and adesired fluid pressure (FP) of the instillation pump 116 for the fluidinstillation therapy phase of the therapy treatment.

After the therapy settings are initialized, the method may furthercomprise a caregiver or patient turning on the therapy system 100 tobegin applying a desired therapy treatment at 604. The desired therapytreatment may include negative pressure therapy, instillation therapy,or other therapy for treating the tissue site as indicated. In someembodiments, for example, the method may comprise applyingnegative-pressure therapy at 605 to the therapy cavity of the dressinginterface to draw fluids from the tissue interface into the therapycavity and exiting out of the reduced-pressure port. The method mayfurther comprise sensing the pH, temperature, humidity, and pressureproperties of the fluids flowing through therapy cavity utilizing thesensing portion of the sensors which may provide property signalsindicative of such properties to the processing element. Applyingnegative-pressure therapy may further comprise providing the propertysignals from the processing element to the controller of the therapysystem for processing the property signals and treating the tissue sitein response to the property data being collected and processed by thetherapy system.

In some embodiments, the method may further comprise applying fluidinstillation therapy at 606 to the therapy cavity of the dressinginterface to provide fluids to the therapy cavity either directly to thetherapy cavity of the dressing interface or indirectly from anotherlocation on the dressing as described above, and ultimately exiting outof the reduced-pressure port. In some embodiments, fluid instillationtherapy may be provided prior to or concurrent with negative pressuretherapy as described in more detail above. The method may furthercomprise sensing the pH, temperature, humidity, and pressure propertiesof the fluids flowing through therapy cavity utilizing the sensingportion of the sensors which may provide property signals indicative ofsuch properties to the processing element. Applying fluid instillationtherapy may further comprise providing the property signals from theprocessing element to the controller of the therapy system forprocessing the property signals and treating the tissue site in responseto the sensor data being collected and processed by the therapy system.

Referring to decision block 607, the method may further comprise turningoff the therapy treatment when receiving a signal from a caregiver, apatient, or from a control algorithm stored on the controller of thetherapy system for assessing the sensor data and corresponding health ofthe tissue site as described in more detail below. If the therapy systemis turned off (YES) ending the therapy treatment at 608, the method mayfurther comprise removing the dressing interface, the cover, and thesensing pad at 609 after the therapy system is turned off as indicated.If no such signal is received to turn off the therapy treatment, themethod in some embodiments may loop back to 605 to continue applying thenegative-pressure therapy with fluid instillation to the dressinginterface and the tissue site. When the method loops back to 605, themethod may include commands provided by the control algorithms tocontinue controlling the negative pressure therapy by increasing thepump pressure (PP) or the pump duty cycle (PD) along with the fluidinstillation therapy by adjusting the instillation pump pressure (IP) orthe instillation duty cycle (ID).

FIG. 11 is a schematic block diagram illustrating an embodiment of acontrol algorithm that may comprise a negative pressure controlalgorithm that may be utilized when applying the negative-pressuretherapy within the tissue treatment method 600, hereinafter referred toas the negative pressure control algorithm 605. The negative pressurecontrol algorithm 605 may include the detection of dressing flowcharacteristics within the system and an assessment of sensor propertiesbased on the property data stored on the controller of the therapysystem. FIGS. 13A-13C show flow charts illustrating various methods ofsome embodiments that may be configured to operate within the negativepressure control algorithm 605 of FIG. 11. The negative pressure therapyalgorithm 605 may commence by initializing the therapy settings at 603including the sensor settings by setting initial values of the propertysignals provided by the sensors to the processing element of thedressing interface and ultimately to the controller of the therapysystem as indicated for processing and assessment.

The negative pressure control algorithm 605 may include a wound pressurecontrol 610 as shown in FIG. 11 that compares wound pressure (WP) to thetarget pressure (TP), and then provides commands to increase or decreasethe pump duty cycle (PD) accordingly and/or log the sensor readings ofthe sensor properties at 650. Referring more specifically to FIG. 13A,if the wound pressure (WP) is greater than the target pressure (TP) at611 (YES), the wound pressure control 610 may generate a command to ventthe therapy cavity at 612 as described above and a command to reduce thepump duty cycle (PD) at 613. After the pump duty cycle (PD) is reduced,the property signals may then be logged in the controller of the therapysystem as indicated at 650 for further processing by a set of assessmentalgorithms as indicated at 651. If the wound pressure (WP) is notgreater than the target pressure (TP) at 611 (NO), the wound pressure(WP) is again compared to the target pressure (TP) at 614. If the woundpressure (WP) is not less than the target pressure (TP), i.e., greaterthan or equal to the target pressure (TP), the wound pressure control610 may generate a command to maintain or reduce the pump duty cycle(PD) at 615 and the property signals may then be logged in thecontroller of the therapy system as indicated at 650 for furtherprocessing by the assessment algorithms 651. However, if the woundpressure (WP) is less than or equal to the target pressure (TP), thewound pressure control 610 may generate a command to increase the pumpduty cycle (PD) at 616. When the pump duty cycle (PD) is increased, thenegative pressure control algorithm 605 in some embodiments may proceedto dressing-alert algorithms including, for example, a blockagedetection algorithm and fluid leak detection algorithm shown generallyat 620 in FIG. 11 (shown more specifically in FIG. 13B), and an air leakdetection algorithm and desiccation detection algorithm shown generallyat 640 in FIG. 11 (shown more specifically in FIG. 13C).

In some embodiments of a therapy system such as, for example, therapysystem 100, the therapy system may comprise a user interface coupled tothe controller 110. Referring more specifically to FIG. 12, a blockdiagram of one example embodiment of a user interface, user interface660, that may comprise a variety of alerts and alarms associated withthe dressing flow characteristics of FIG. 11. These alerts and/or alarmsassociated with the dressing flow characteristics may comprise, forexample, alerts and/or alarms for a blockage condition 661, a fluid leakcondition 662, an air leak condition 663, or a desiccation condition664. The negative pressure control algorithm may be programmed togenerate an alarm based on the occurrence of a predetermined number ofalerts such as, for example, generating alarm after the occurrence ofthree alerts. The user interface 660 may also provide alerts and/oralarms that may be associated with wound progress 665 and/orcanister-full alert 667 based on the fluid properties being provided bythe sensing pad or the dressing interface 400, for example. All of thefluid properties and associated alerts and/or alarms identified abovemay be selectively provided for each wound dressing (WD #1, WD #2 or WD#3) such as, for example, wound dressings substantially similar to thedressing 102, that may be fluidly and electrically coupled to thetherapy system 100. For example, a patient or caregiver may select adesired wound dressing by setting a wound dressing selection switch 668.Alternatively, the controller of the therapy system may be programmed toselectively collect the fluid properties and provide alerts and/oralarms based on a predetermined order with times designated for eachwound dressing.

After the negative pressure control algorithm 605 proceeds to thedressing-alert algorithms including, for example, the blockage detectionalgorithm and fluid leak detection algorithm shown generally at 620 inFIG. 13B, the algorithm may commence with determining whether the woundpressure (WP) is increasing at 621 after increasing the pump duty cycle(PD) at 616 by a predetermined increment as an output of the woundpressure control 610. If the wound pressure (WP) responds and isincreasing, the algorithm may increment an air leak counter at 622 andproceed to the air leak detection algorithm and desiccation detectionalgorithm at 640. However, if the wound pressure (WP) does not increase,the blockage/leak detection algorithm 620 determines whether theproperty signals associated with the humidity, i.e., the humidity data,is rising at a relatively low rate within the therapy cavity at 623. Ifthe humidity data is rising at a relatively low rate, the blockage/leakdetection algorithm 620 increments a blockage counter 624 and inquireswhether the blockage counter is less than a predetermined blockage countthreshold at 625 such as, for example, less than three, to determinewhether a blockage alert or alarm should be generated. If the blockagecounter number is less than the blockage count threshold, theblockage/leak detection algorithm 620 generates a blockage alert at 626and progresses to log a new set of sensor readings at 650. If theblockage counter number is greater than or equal to the blockage countthreshold, the negative pressure control algorithm generates a blockagealarm at 627 and progresses to log a new set of sensor readings at 650.

If the humidity data is not rising at a relatively low rate at 623, thenegative pressure control algorithm inquires whether the humidity datais increasing at a high rate at 628. If the humidity data is notincreasing at such a high rate, the blockage/leak detection algorithm620 increments the air leak counter 622 and proceeds to the air leakdetection algorithm and desiccation detection algorithm at 640. However,if the humidity data is increasing above the high rate, theblockage/leak detection algorithm 620 increments or increases a fluidleak counter at 629 and inquires whether the fluid leak counter is lessthan a predetermined leakage count threshold at 630 such as, forexample, less than three. If the fluid leak counter number is not lessthan the leakage count threshold, alternatively greater than or equal tothe leakage count threshold, the blockage/leak detection algorithm 620generates a fluid leak alarm at 631 and progresses to log a new set ofsensor readings at 650. If the fluid leak counter number is less thanthe leakage count threshold, the blockage/leak detection algorithm 620checks the dead space detection at 632 that may be associated with theamount of gas or space that may be present in the container of thetherapy system such as, for example, the container 112, after collectingliquids in the container. The blockage/leak detection algorithm 620determines whether there is a dead space detection variance of less thana predetermined value, e.g., 200 cc, at 633. If the variance is not lessthan the predetermined value, i.e., if the variance is greater than thepredetermined value, the blockage/leak detection algorithm 620 generatesa fluid leak alarm at 631. If the blockage/leak detection algorithm 620determines that the variance is less than the predetermined value, theblockage/leak detection algorithm 620 generates a canister full alert667 (not shown in FIG. 13A) and then progresses to log a new set ofsensor readings at 650.

After the negative pressure control algorithm 605 proceeds to thedressing-alert algorithms including, for example, the air leak detectionalgorithm and desiccation detection algorithm at 640, or adesiccation/leak detection algorithm, shown generally at 640 in FIG.13C, the algorithm may commence by determining at 641 whether the airleak counter at 622 is less than a predetermined air count threshold at641 such as, for example, less than three, after incrementing the airleak counter as described above. If the air leak counter 641 is lessthan the air count threshold, the negative pressure control algorithmmay generate an air leak alert at 642 and progress to log a new set ofsensor readings at 650. If the air leak counter 641 is not less than theair count threshold, alternatively if the air leak counter is greaterthan or equal to the air count threshold, the desiccation/leak detectionalgorithm 640 may generate an air leak alarm at 643 and proceed toinquire whether the humidity is less than about a predetermined internalhumidity value at 644. More specifically, if the humidity within thetherapy cavity of the sensing pad measured by the humidity sensor 418 isless than a percentage value of the ambient humidity (ambient humiditysensor not shown) such as, for example, a percentage value of 25%, thedesiccation/leak detection algorithm 640 may generate a desiccationalert at 645 and proceed to log new set of sensor readings at 650.Alternatively, if the humidity within the therapy cavity of the sensingpad is greater than a humidity percentage of 25%, for example, thedesiccation/leak detection algorithm 640 would not generate adesiccation alert, but rather would proceed to log new set of sensorreadings at 650.

Referring back to FIG. 11, a new set of property signals indicative ofthe sensor properties may be logged at 650 into the controller of thetherapy system as a result of the alerts, alarms, and other eventsdescribed above with respect to the negative pressure control algorithm605 including the wound pressure control 610, the blockage detection andfluid leak detection algorithms 620, and the air leak detectionalgorithm and desiccation detection algorithm at 640. Logging theseproperty signals along with contemporaneous readings of the woundpressure (WP), the pump pressure (PP), and the pump duty cycle (PD)generates sets of property data that may include humidity data,temperature data, and pH data being provided by the processing elementsuch as, for example, the sensor assembly 425 in addition to thepressure data, duty cycle data, and other data that might be availablefrom other sensors in the therapy system 100. Such other sensors alsomay be coupled to the controller or other distribution components in thetherapy system. In some embodiments, the negative pressure controlalgorithm 605 may be configured to assess the pH data at 652, thehumidity data at 654, and the temperature data at 656, and use such datato assess the status of wound health of the tissue site at 658, andfurther configured to return to the wound pressure control 610 after theassessments have been completed. In some embodiments, the assessmentsmay include an analysis of whether the data is increasing or decreasingand how rapidly the data may be increasing or decreasing. In someembodiments, the assessments may further include an analysis of whetherthe data may increase or decrease and how rapidly that data mayfluctuate in each direction. In some embodiments, the assessment mayfurther include a determination that the relevant data is simply notaffected.

The assessments of the pH data, the humidity data, and the temperaturedata along with contemporaneous wound pressure (WP) data, pump pressure(PP) data, and the pump duty cycle (PD) data may be utilized todetermine how the flow characteristics of the therapy system 100 may beaffected by a blockage, a fluid leak, an air leak, or desiccation withinthe system including the sensor pad or dressing interface 400. Referringmore specifically to Table 1, the flow characteristics may include ablockage state condition within the therapy system that may beidentified by the assessment of the pH data, the humidity data, and thetemperature data along with contemporaneous wound pressure (WP) data,pump pressure (PP) data, and the pump duty cycle (PD) data.

TABLE 1 Dressing State: Flow Characteristics Inputs Blockage Fluid Leak(Bolus) Air Leak Wound Pressure WP may slowly decrease WP will decreaseWP may decrease (WP)  

   

   

  Sensor Assembly Wound Humidity Humidity may Humidity will Humidity maychange (Hum) increase slowly increase rapidly  

   

   

  Sensor Assembly Wound Temperature Temperature may increase Temperaturemay Temperature may (Temp) slowly increase change Sensor Assembly  

   

   

  Pump Duty PD will increase PD may increase PD will increase (PD)  

   

   

  System Pump Pressure PP will increase PP may increase for PP mayincrease (PP)  

  a short time  

  System  

 

For example, a blockage state condition may be identified in the system(e.g., a substance blocking a tube or a kink in the tube) when the pumppressure (PP) data increases and the pump duty cycle (PD) dataincreases. In some embodiments, the blockage state condition may beidentified further if the wound pressure (WP) data slowly decreases. Inyet other embodiments, the blockage state condition may be identifiedfurther if the humidity data slowly increases, especially if the wounddressing is saturated with fluids. In yet other embodiments, theblockage state condition may be identified further if the temperaturedata slowly increases. In still other embodiments, the blockage statecondition may be identified further when the pH data is not affected.Referring to FIG. 14 as an example, a graph is shown illustrating testresults using the dressing interface 400 for the detection of blockagesbased on the assessment of humidity data and wound pressure over timegenerated by the negative pressure control algorithm 605 of FIG. 11. Thewound pressure (WP) being applied at the tissue site is set as a targetpressure (TP) of 125 mmHg. As can be seen, a blockage state condition isidentified at approximately 1.50 minutes when the wound pressure (WP)701 begins to decrease and the dressing humidity 702 slowly increasesover the ambient humidity 703 as described above. In some embodiments,the negative pressure control algorithm 605 may generate a command toprovide an alarm 661 and shut down the pump 104, for example, until theblockage can be removed. When the blockage is removed at 3.67 minutes,the wound pressure (WP) returns to the target pressure (TP) and thedressing humidity converges back to the ambient humidity.

Still referring more specifically to Table 1, the flow characteristicsmay include a fluid leak state within the therapy system that also maybe identified by the assessment of the pH data, the humidity data, andthe temperature data along with contemporaneous wound pressure (WP)data, pump pressure (PP) data, and the pump duty cycle (PD) data. Forexample, a fluid leak state may be identified in the wound dressing ifthe pump duty cycle (PD) data and the pump pressure (PP) data increasedepending on the severity of a fluid bolus trapped in the wounddressing. The pump pressure (PP) data may increase for only a shortperiod of time. In some embodiments, the fluid leak state may beidentified further if the wound pressure (WP) data decreases but willtypically track with the pump pressure (PP) data. In yet otherembodiments, the fluid leak state may be identified further if thehumidity data increases as a result of higher exudates or blood volumescollecting at the tissue site. The temperature data may also increase ina corresponding fashion. In still other embodiments, the fluid leakstate may be identified further when the pH data is not affected.Referring to FIG. 15 as an example, a graph is shown illustrating testresults using the dressing interface 400 for the detection of fluidleaks based on the assessment of humidity data and wound pressure dataover time generated by the negative pressure control algorithm of FIG.11. The wound pressure (WP) being applied at the tissue site is set as atarget pressure (TP) of 125 mmHg. A bolus of 60 cc of simulated woundfluid with a viscosity of about 16 cP was rapidly introduced into thewound dressing. As can be seen, a fluid leak state is identified atapproximately 0.50 minutes when the wound pressure (WP) 711 begins todecrease and the dressing humidity 712 slowly increases over the ambienthumidity 713 as described above. In some embodiments, the negativepressure control algorithm 605 may generate a command to provide analarm 662 and shut down the pump 104, for example, until the fluid leakcan be corrected. Clearly, such assessment facilitates the detection ofliquid boluses or potentially adverse events such as a blood vessel thatbursts, so that a caregiver may be alerted to a potentially dangeroussituation so that a timely intervention is possible.

Referring more specifically to Table 2, the flow characteristics mayinclude an air leak state within the therapy system that may beidentified by the assessment of the pH data, the humidity data, and thetemperature data along with contemporaneous wound pressure (WP) data,pump pressure (PP) data, and the pump duty cycle (PD) data.

TABLE 2 Dressing State: Flow Characteristics Inputs Air Leak DesiccationWound Pressure WP may decrease WP likel unaffected (WP)  

   

  Sensor Assembly Wound Humidity Humidity may change Humidity will (Hum)rapidly decrease  

   

  Sensor Assembly Wound Temperature Temperature may Temperature may(Temp) change change Sensor Assembly  

   

  Pump Duty PD will increase PD likely unaffected (PD)  

   

  System Pump Pressure PP may increase PP likely unaffected (PP)  

   

  System

For example, an air leak state within the therapy system that may beidentified when the pump duty cycle (PD) data increases proportionallywith the severity of the leak, and wherein the pump pressure (PP) datamay increase or nonresponsive to an increase in the pump duty cycle (PD)data again depending on the severity of the leak. The air leak may besufficiently severe to require an increase in both the pump duty cycle(PD) and the pump pressure (PP). In some embodiments, the air leak statemay be identified further if the wound pressure (WP) begins to decreaseproportionally with the severity of the leak but will track with thepump pressure (PP). In yet other embodiments, the air leak state may beidentified further if the humidity data changes rapidly depending uponthe environmental humidity measured by the system and the saturationlevel of the wound dressing. For example, if the air is drier than thesaturation level of the wound dressing, then the humidity of thedressing may decrease. The air leak state may also be identified furtherif the temperature data changes depending on the environmentaltemperature and the saturation level of the wound dressing. For example,the temperature data will decrease if the environmental temperature iscooler than the temperature at the tissue site. In still otherembodiments, the air leak state may be identified further when the pHdata is not affected. Referring to FIG. 16 as an example, a graph isshown illustrating test results using the dressing interface 400 for thedetection of air leaks based on the assessment of humidity data, woundpressure data, and pump pressure data over time generated by thenegative pressure control algorithm of FIG. 11. The wound pressure (WP)being applied at the tissue site is set as a target pressure (TP) of 125mmHg. A small leak was introduced into the wound dressing such that thepump pressure (PP) had to be elevated to approximately 140 mmHg in orderto maintain a wound pressure (WP) at the target pressure (TP). As can beseen, an air leak state is identified at approximately 0.2 minutes whenthe wound pressure (WP) 721 decreases and the pump pressure (PP) 722increases to compensate for the decreasing wound pressure (WP). In someembodiments, the air leak state also may be identified by the dressinghumidity 723 which slowly increases to converge with the ambienthumidity 724. In this example, the tissue interface was dry, so that thehumidity increased with the introduction of the leak (ambient humidity).In other embodiments, the air leak state also may be identified by thedressing humidity 723 which slowly decreases to converge with theambient humidity 724.

In some embodiments where the humidity data decreases indicating thatthe wound is drying out, the negative pressure control algorithm 605 maygenerate a command to provide an alarm 663 and shut down the pump 104until the air leak can be corrected. In other embodiments where thehumidity does not decrease or is at an acceptable level, the negativepressure control algorithm 605 may generate a command to provide analarm or an alert 663 but continue providing therapy by increasing thepump duty cycle (PD) to compensate for the air leak. Referring back toTable 1, an air leak state may be distinguished from a fluid leak statebecause the humidity data will increase in the presence of a fluid leakbut will not increase in the presence of an air leak (although it mayfluctuate rapidly). Clearly, such assessment facilitates the detectionof air leaks by differentiating them from fluid leaks, so that thetherapy system may continue providing negative pressure therapy byincreasing the pump duty cycle (PD) to compensate for the air leakrather than discontinuing the therapy being provided.

Still referring more specifically to Table 2, the flow characteristicsmay include a desiccation state within the wound dressing that also maybe identified by the assessment of the pH data, the humidity data, andthe temperature data along with contemporaneous wound pressure (WP)data, pump pressure (PP) data, and the pump duty cycle (PD) data. Forexample, a desiccation state may be identified if the pump pressure (PP)data and the pump duty cycle (PD) data remain unchanged, unless there isan air leak present which causes a moisture drop. In some embodiments,the desiccation state may be identified further if the wound pressure(WP) the also remains unchanged, unless there is an air leak present. Inyet other embodiments, the desiccation state may be identified furtherif the humidity data decreases longitudinally over time. The humiditydata may be tracked and compared to a minimum threshold value to preventor avoid wound desiccation. The negative pressure control algorithm maybe configured to provide an alert and/or an alarm in the event that thehumidity data falls below the minimum threshold value. In still otherembodiments, the desiccation state may be identified further if the pHdata decreases slightly as the tissue site becomes slightly more acidicfrom drying. The temperature data also may change based on drying andthe lack of sufficient exudation of the at the tissue site. Referring toFIG. 17 as an example, a graph is shown illustrating test results usingthe dressing interface 400 for the detection of desiccation conditionsbased on the assessment of humidity data over time generated by thenegative pressure control algorithm of FIG. 11. The tissue interfacesuch as, for example, tissue interface 108, was filled in saturated withsimulated wound fluid. After the tissue interface was saturated with thewound fluid, the wound pressure (WP) was set as a target pressure (TP)of 125 mmHg and applied to the tissue interface. As can be seen, adesiccation state may be identified a decreasing dressing humidity 731compared to the ambient humidity by tracking the humidity data andcomparing it to a minimum threshold value as described above. In someembodiments, the negative pressure control algorithm 605 may generate acommand to provide an alert 664 and shut down the pump 104, for example,until the desiccation can be corrected.

The assessments of the pH data at 652, the humidity data at 654, and thetemperature data at 656 along with contemporaneous wound pressure (WP)data, pump pressure (PP) data, and the pump duty cycle (PD) data may beutilized to assess the health of the wound at 658 including, forexample, the progression of wound healing, i.e., the wound status.

TABLE 3 Wound Status: Inputs Wound Health/Progression Wound PressureCritically affected (WP) (May Increase or Decrease) Wound Humidity Mayincrease or decrease (Hum) slowly Wound pH Will change with woundregression or progression (May Increase or Decrease) Wound May increaseor decrease Temperature slowly (Temp)

Referring more specifically to Table 3, the wound status may include adetermination of the progression of wound healing that may be identifiedby the assessment of the pH data, the humidity data, and the temperaturedata along with contemporaneous wound pressure (WP) data, pump pressure(PP) data, and the pump duty cycle (PD) data. For example, a woundhealing state may be identified when the pH data changes in response towound healing regression or progression. For example, in someembodiments, the wound may be considered in a healthy state if the woundfluids have a pH of approximately 7.4 and the pH data indicates that thepH has held at that value over a predetermined time period. In someother embodiments, the wound may be considered in a healthy state if thewound fluids have a pH that stays within a range from about 5.0 to about8.0 and remains within that range over a predetermined time period. Morespecifically, if the pH data exceeds 8.0, the wound may be considered tobe in a chronic state. Additionally, if the pH data is less than about6.0, the wound may be considered to be in an inflammatory state. In someembodiments, the wound healing state may be identified when the humiditydata and the temperature data both increase or decrease slowly atpredetermined rates. For example, if the temperature data indicates thatthe temperature is increasing, the increasing temperature may be anindication that the wound is infected. Additionally, the wound pressure(WP) or the pump pressure (PP) may critically affect the healingprogression or regression. For example, if the pressure is not withinthe therapeutic range that was prescribed, then the patient is notgetting the benefit of the therapy. However, wound progression orregression does not necessarily affect the wound pressure (WP) or thepump pressure (PP). In some embodiments, the negative pressure controlalgorithm 605 may generate a command to provide an alert 665 andcontinue providing therapy including, for example, the instillation offluids that may include medication until the pH returns to an acceptablerange.

FIG. 18 is a schematic block diagram illustrating an embodiment of acontrol algorithm that may comprise a fluid instillation controlalgorithm that may be utilized when applying the fluid instillationtherapy 606 within the tissue treatment method 600, hereinafter referredto as the fluid instillation control algorithm 706. The fluidinstillation control algorithm 706 may include the detection of dressingflow characteristics within the system and an assessment of sensorproperties based on the property data stored on the controller of thetherapy system. FIGS. 19A-19B show flow charts illustrating variousmethods of some embodiments that may be configured to operate within thefluid instillation control algorithm 706 of FIG. 18. The fluidinstillation therapy algorithm 706 may commence by initializing thetherapy settings at 603 including logging the baseline readings of thesensors at 703 and setting the initial values of the property signalsprovided by the sensors. In some embodiments, the property signals maybe sent to the processing element of the dressing interface andultimately to the controller of the therapy system as indicated forprocessing and assessment.

A tissue interface such as the tissue interface 108 may be placedwithin, over, on, or otherwise proximate a tissue site as describedabove, and may include an accelerometer or other device for determiningwhether the sensors within the dressing interface are properly orientedat the tissue site. The fluid instillation control algorithm 706 mayinclude a dressing orientation process at 708 that processes data fromthe accelerometer to determine whether sensors in the dressing interfaceare correctly oriented with respect to the tissue interface at thetissue site. If the sensors are not correctly oriented (NO), the fluidinstillation control algorithm 706 in some embodiments may proceed to adressing-fill assist subroutine at 710 shown more specifically in FIG.19A. When the dressing-fill assist subroutine is completed, the sensorreadings may be logged and assessed at 720 along with a measurement ofthe amount of fluid dispensed to the tissue interface, i.e., thedispensed fill volume, as a result of the dressing-fill assistsubroutine. After the sensor readings and the dispensed fill volume havebeen logged and assessed, the fluid instillation control algorithm 706may further comprise providing wound pressure alerts at 721 similar tothose described above.

Referring back to 708, if the tissue interface is correctly oriented(YES), the fluid instillation control algorithm 706 in some embodimentsmay proceed to a pump control routine the compares the relative dressinghumidity to a target humidity, and then provides commands to start orstop the instillation pump depending on the results of the comparison.More specifically, the pump control routine may compare the relativedressing humidity to the target humidity at 722 and stop theinstillation pump at 723 (YES) if the relative dressing humidity exceedsthe target humidity. After the instillation pump has been stopped at723, the sensor readings and the dispensed fill volume may be logged andassessed at 720 and wound pressure alerts may be provided at 721. Thepump control routine may include a redundant check of the role dressinghumidity in comparison to the target humidity at 724 and stop theinstillation pump at 725 (NO) if the relative dressing humidity is lessthan the target humidity. After the instillation pump has been stoppedat 725, the sensor readings and the dispensed fill volume may be loggedand assessed at 720 and wound pressure alerts may be provided at 721.Thus, if the relative dressing humidity is not greater than the targethumidity at 722 and less than the target humidity at 724, then the fluidinstillation control algorithm 706 in some embodiments may proceed todressing-alert algorithms including, for example, a blockage detectionalgorithm and fluid leak detection algorithm shown generally at 730shown more specifically in FIG. 19B. After either a blockage or dressingleak has been identified, the fluid instillation control algorithm 706in some embodiments may log the sensor readings at 750 and loop back to722 for further comparisons of the relative dressing humidity to thetarget humidity. However, if the relative dressing humidity is greaterthan the target humidity at 722 and not less than the target humidity at724, the pump may be stopped to log and assess the sensor readings andthe dispensed volume.

After the fluid instillation control algorithm 706 proceeds to thedressing-alert algorithms including, for example, the blockage detectionalgorithm and fluid leak detection algorithm shown generally at 730 inFIG. 19A, the algorithm may provide a command to continue operating theinstillation pump at 731 and proceed to determine whether the relativedressing humidity is increasing at 732. If the relative dressinghumidity is not increasing (NO), the fluid instillation controlalgorithm 706 may proceed to determine whether the duty cycle (ID) ofthe instillation pump is increasing at 733. The algorithm may proceed toimplement the fluid leak detection algorithm if the duty cycle (ID) isnot increasing (NO), or to implement the blockage detection algorithm ifthe duty cycle (ID) is increasing (YES). When the fluid instillationalgorithm proceeds with the blockage detection algorithm, the algorithmmay increment a blockage counter at 734 and proceed to determine whetherthe blockage counter is less than a predetermined blockage countthreshold at 735 such as, for example, less than three increments todetermine whether a blockage alert or alarm should be generated. If theblockage counter is less than the blockage count threshold, the blockagedetection algorithm may generate a blockage alert at 736 and proceed tolog a new set of sensor readings at 750, e.g., pH, temperature, andhumidity readings. If the blockage counter number is greater than orequal to the blockage count threshold, the blockage detection algorithmmay generate a blockage alarm at 737 and proceed to log a new set ofsensor readings at 750. The blockage detection algorithm may then loopback to check the relative dressing humidity with respect to the targethumidity at 722 as described above.

As indicated above, the fluid instillation control algorithm may proceedto implement the fluid leak detection algorithm if the duty cycle (ID)of the instillation pump is not increasing (NO) at 733 and proceed toincrement a leakage counter at 738. The leakage detection algorithm maythen proceed to determine whether the leakage counter is less than apredetermined leakage count threshold at 740 such as, for example, lessthan three increments to determine whether a leakage alert or alarmshould be generated. If the fluid leak counter is not less than theleakage count threshold, alternatively greater than or equal to theleakage count threshold, the leak detection algorithm may generate afluid leak alarm at 741 and proceed to log a new set of sensor readingsat 750. However, if the fluid leak counter number is less than theleakage count threshold, the leak detection algorithm may generate adressing leak alert at 742 and proceed to check a dead space detectionalgorithm at 743 that may be associated with the amount of gas or spacethat may be present in the tissue interface of the dressing such as, forexample, the tissue interface 108 of the dressing 102 after instillingliquids into the tissue interface. The leak detection algorithm maydetermine whether there is a dead space detection variance of less thana predetermined value, e.g., 200 cc, at 744. If the variance is not lessthan the predetermined value, i.e., if the variance is greater than thepredetermined value, the leak detection algorithm may generate a fluidleak alarm at 741. If the leak detection algorithm may determine thatthe variance is less than the predetermined value, the leak detectionalgorithm may generate a canister-full alert 667 (not shown in FIG. 19A)and then proceed to log a new set of sensor readings at 750. Returningback to the decision at 732 of the fluid instillation control algorithm,the algorithm proceeds to log a new set of sensor readings at 750 if therelative dressing humidity is increasing and then loops back to checkthe relative dressing humidity with respect to the target humidity at722 as described above.

Referring back to FIG. 18, the fluid instillation control algorithm 706may further comprise a fill assist algorithm 710 that may facilitatedetermining whether the tissue interface has been instilled with avolume of fluids desired for the instillation therapy, i.e., a desiredfill volume. Referring more specifically to FIG. 19B, the fill assistalgorithm 710 may comprise a dead space detection algorithm 711 that maybe similar to the dead space detection algorithm 743 described above.The fill assist algorithm 710 may then proceed to provide a command to acontroller to evacuate a therapy cavity of a dressing interface such as,for example, the controller 110 evacuating the therapy cavity 403 of thedressing interface 400, to a negative pressure sufficient to commenceinstillation of the fluids at 712. For example, a negative pressure ofabout 25 mmHg, which is well below the negative pressure therapy levelof negative pressure, may be applied to the therapy cavity to commenceinstillation of the fluids. The negative pressure may be provided by thesuction of a negative pressure pump such as, for example, the negativepressure pump 104, as described in more detail above.

In some embodiments, providing this suction may be sufficient forinstilling fluid into the therapy cavity. In other embodiments, aninstillation pump such as, for example, the instillation pump 116, maybe used in conjunction with the suction to commence instillation. Forexample, the instillation pump may provide a positive force to instillthe fluids into the therapy cavity as shown at 713 and may besupplemented by continuing to provide negative pressure from thenegative pressure pump. The fill assist algorithm 710 may also include apressure check algorithm at 714 for determining whether pressure changeswithin the therapy cavity are within an acceptable range, whileinstilling fluids into the therapy cavity and allowing those fluids tosoak for a desirable so time. If the pressure measured is not within theacceptable range (NO), the fill assist algorithm 710 may generate adressing leak alarm at 741. However, if the pressure measured is withinthe acceptable range (YES), the fill assist algorithm 710 may provide acommand to a controller to generate a command to open a pressure reliefvalve at 715 such as, for example, the controller 110 generating acommand to the regulator 118 as described above, in order to furtherevacuate gases from the therapy cavity and draw liquids into the therapycavity. The controller may be programmed to open the pressure reliefvalve for a fill period sufficient to provide the therapy cavity and thetissue interface with a desired fill volume. The fill assist algorithm710 may also continue providing fill assist at 716 by refilling thetherapy cavity until previous fill volumes are achieved for anothercycle of instillation therapy. Whenever the desired fill volume or fillvolumes are achieved, the fill assist algorithm 710 may proceed back tothe fluid instillation control algorithm 706 so that the sensor readingsmay be logged and assessed at 720 along with a measurement of the amountof fluid dispensed to the tissue interface, i.e., the dispensed fillvolume. After the sensor readings and the dispensed fill volume havebeen logged and assessed, the fluid instillation control algorithm 706may continue by providing wound pressure alerts at 721 similar to thosedescribed above.

Referring back to FIG. 18, a new set of sensor readings indicative ofthe sensor properties and dispensed volumes may be logged at 720 intothe controller of the therapy system as a result of the alerts, alarms,and other events described above with respect to the fluid instillationcontrol algorithm 706 including the dressing orientation control 708,the fill assist algorithm 710, and the blockage detection and fluid leakdetection algorithms 730. Logging these property signals along withcontemporaneous readings of the wound pressure (WP), the instillationpump pressure (IP), and the instillation pump duty cycle (ID) generatessets of property data that may include humidity data, temperature data,and pH data being provided by the processing element such as, forexample, the sensor assembly 425, in addition to the pressure data, dutycycle data, and other data that might be available from other sensors inthe therapy system 100. Such other sensors also may be coupled to thecontroller or other distribution components in the therapy system. Forexample, some embodiments may include an occlusion sensor (not shown),such as the fluid connections located in the therapy device shown inFIG. 1, that independently checks the possibility of a blockage or kinkin the conduits or tubing coupled to the dressing interface. In someembodiments, the fluid instillation control algorithm 706 may beconfigured to assess the pH data, the humidity data, the temperaturedata, and the dispensed volume of fluids, and then use such assessmentdata to evaluate the status of wound health of the tissue site at 721.The fluid instillation control algorithm 706 may be configured furtherto return to the wound pressure control algorithm 605 after suchassessments have been completed. In some embodiments, the assessmentsmay include an analysis of whether the data is increasing or decreasingand how rapidly the data may be increasing or decreasing. In someembodiments, the assessment may further include a determination that therelevant data is simply not affected

The assessments of the pH data, the humidity data, the temperature data,and the dispensed volume data, along with contemporaneous wound pressure(WP) data, instillation pump pressure (IP) data, and the instillationpump duty cycle (ID) data may be utilized to determine how the flowcharacteristics of the therapy system 100 may be affected by a blockage,a fluid leak, or a full canister within the system including the sensorpad or dressing interface 400. Referring more specifically to Table 4and FIG. 20, the flow characteristics may include a blockage statecondition within the therapy system that may be identified by theassessment of the humidity data and the temperature data of the tissuesite or the wound, along with contemporaneous wound pressure (WP) data,instillation pump pressure (IP) data, the instillation pump duty cycle(ID) data, and the occlusion sensor.

TABLE 4 Dressing State: Flow Characteristics Inputs Blockage Fluid Leak(Bolus) Fill Status Wound Pressure WP may increase WP may not change WPmay increase (WP)  

   

  Sensor Assembly Wound Humidity Humidity will not Humidity may notincrease Humidity will increase (Hum) increase  

  Sensor Assembly Wound Temperature Temperature will Temperature maydecrease Temperature will decrease (Temp) not decrease  

   

  Sensor Assembly Instillation Pump Duty ID will increase ID will notincrease N/A (ID)  

  System Instillation Pump Pressure IP will increase IP may increase N/A(IP)  

   

  System Occlusion Sensor (System) May trip N/A N/A

For example, a blockage state condition may be identified in the system(e.g., a substance blocking a tube or a kink in the tube) when theinstillation pump pressure (IP) data increases and the instillation pumpduty cycle (ID) data increases. In some embodiments, the blockage statecondition may be identified further if the relative dressing humiditydoes not increase toward a target humidity such as, for example, atarget humidity threshold which in some embodiments corresponds to acondition of the tissue interface being instilled to a desired fillvolume. FIG. 20 is a graph illustrating an instillation response curve760 including data associated with the relative humidity percentage of adressing in response to the fluid instillation control algorithm of FIG.18. The graph includes, for example, a target humidity threshold 762that is about 90% which may be determined to be an indication that thetissue interface is fully saturated with fluids as a result ofinstilling the desired fill volume. In this example, the relativehumidity data is increasing at 761 of the response curve 760 toward thetarget humidity threshold 762 so that a blockage condition might notexist apart from other information. In yet other embodiments, theblockage state condition may be identified further if the temperaturedata does not decrease. For example, in some embodiments the temperaturedata does not decrease because the fluid simply does not reach into thetissue interface. Normally, the body temperature of the patient iswarmer than the temperature of the fluids being instilled so that thetemperature of the instillation fluid should drop if the fluid reachedthe tissue interface. In some other embodiments, the blockage statecondition may be identified further if the wound pressure (WP)increases. In still other embodiments, the blockage state condition maybe identified further when the occlusion sensor located in the fluidconduits of the therapy device is tripped. In some embodiments, thefluid instillation control algorithm 706 may generate a command toprovide an alarm 661 and shut down the pump 116, for example, until theblockage can be removed, and the relative dressing humidity begins toincrease toward the target humidity threshold such as, for example,toward 90% as shown in FIG. 20.

Still referring more specifically to Table 4, the flow characteristicsmay include a fluid leak state within the therapy system that also maybe identified by the assessment of the humidity data and the temperaturedata, along with contemporaneous wound pressure (WP) data, instillationpump pressure (IP) data, the instillation pump duty cycle (ID) data, andthe occlusion sensor. For example, a fluid leakage state may beidentified in the wound dressing if the instillation pump duty cycle(ID) data does not increase. This may result from a fluid bolus trappedin the wound dressing that does not fill the therapeutic cavity, aclosed volume, resulting in the lack of a back pressure that should haveresulted from filling the therapeutic cavity. In some embodiments, thefluid leak state may be identified further if the humidity dataincreases but does not increase fully toward the target thresholdhumidity of 90% to satisfy an assessment that the tissue interface isfull. In still other embodiments, the fluid leak state may be identifiedfurther if the temperature data changes depending on the size of theleak. For example, if the body temperature is warmer than thetemperature of the instillation fluid, then the temperature of theinstillation fluid will decrease provided that the fluid does contactthe tissue interface before leaking out of the dressing. In someembodiments, the fluid instillation control algorithm 706 may generate acommand to provide an alarm 662 and shut down the pump 116, for example,until the fluid leak can be corrected. Clearly, such assessmentfacilitates the detection of liquid boluses or potentially adverseevents such as a blood vessel that bursts with the addition ofinstillation fluid in a fixed volume, so that a caregiver may be alertedto a potentially dangerous situation and/or the controller can quicklyshut down the pump 116.

Still referring to Table 4, the flow characteristics may include adressing fill status for the therapy system to assist a caregiver by theassessment of the humidity data and the temperature data, along withcontemporaneous wound pressure (WP) data. For example, a dressing fillstatus may be identified in the wound dressing if the humidity dataincreases to the target threshold humidity such as, for example, towardthe 90% humidity as shown in FIG. 20 indicating that the therapy cavityand/or the tissue interface is saturated with the instillation liquid asmetered out by desired fill volume. In some embodiments, the fluidinstillation control algorithm 706 may generate a command to provide acanister full alert 667 and/or shut down the pump 116, for example,because the relative dressing humidity increased to a target humiditythreshold such as, for example, 90% to detect a fully saturated dressingat a predetermined desired fill volume of about 38 ml at 764. Once thedressing is fully saturated to this predetermined value, the relativedressing humidity remains substantially constant as shown by the flatportion 763 of the response curve 760. In still other embodiments, adressing fill status may be identified if the temperature decreases asinstillation fluid is introduced into the dressing. For example, if thebody temperature is warmer than the temperature of the instillationfluid, then the temperature of the instillation fluid will decreaseprovided that the fluid does contact the tissue interface before leakingout of the dressing. In yet other embodiments, a dressing fill statusmay be identified if the wound pressure (WP) increases to a pressureslightly higher than the ambient pressure, or if the wound pressure (WP)does not increase or decrease after the dressing is saturated with theinstillation fluids. Such assessment facilitates the identification of adressing fill status to assist a caregiver's visual monitoring of thedressing so that the caregiver may be alerted to a potentially dangeroussituation and the controller can quickly shut down the relation pump 116after the desired fill volume has been achieved.

While shown in a few illustrative embodiments, a person having ordinaryskill in the art will recognize that the systems, apparatuses, andmethods described herein are susceptible to various changes andmodifications. For example, certain features, elements, or aspectsdescribed in the context of one example embodiment may be omitted,substituted, or combined with features, elements, and aspects of otherexample embodiments. Moreover, descriptions of various alternativesusing terms such as “or” do not require mutual exclusivity unlessclearly required by the context, and the indefinite articles “a” or “an”do not limit the subject to a single instance unless clearly required bythe context. Components may be also be combined or eliminated in variousconfigurations for purposes of sale, manufacture, assembly, or use. Forexample, in some configurations the dressing 102, the container 112, orboth may be eliminated or separated from other components formanufacture or sale. In other example configurations, the controller 110may also be manufactured, configured, assembled, or sold independentlyof other components.

The appended claims set forth novel and inventive aspects of the subjectmatter described above, but the claims may also encompass additionalsubject matter not specifically recited in detail. For example, certainfeatures, elements, or aspects may be omitted from the claims if notnecessary to distinguish the novel and inventive features from what isalready known to a person having ordinary skill in the art. Features,elements, and aspects described herein may also be combined or replacedby alternative features serving the same, equivalent, or similar purposewithout departing from the scope of the invention defined by theappended claims.

What is claimed is:
 1. A system for controlling negative pressuretherapy with fluid instillation therapy using properties of fluids at atissue site, the system comprising: a tissue interface adapted to bedisposed at a tissue site and adapted to be coupled to a source ofinstillation fluid; and a dressing interface adapted to couple a sourceof negative-pressure to the tissue interface, the dressing interfacecomprising: a housing having a therapy cavity including an openingconfigured to be disposed in fluid communication with the tissueinterface, and a negative-pressure port adapted to fluidly couple thetherapy cavity to the source of negative-pressure; a pressure sensormounted to the housing in fluid communication with the therapy cavityand configured to sense the pressure of fluids adjacent the tissueinterface during instillation of liquids to the tissue interface; ahumidity sensor mounted to the housing in fluid communication with thetherapy cavity and configured to sense the humidity of fluids adjacentthe tissue interface during instillation of liquids to the tissueinterface; a temperature sensor mounted to the housing in fluidcommunication with the therapy cavity and configured to sense thetemperature of fluids adjacent the tissue interface during instillationof liquids to the tissue interface; and a processing elementelectrically coupled to the pressure sensor, the humidity sensor, andthe temperature sensor for receiving property signals indicative of thepressure, humidity, and temperature, the processing element beingconfigured to determine flow characteristics of the system.
 2. Thesystem of claim 1, wherein the therapy cavity further comprises a ventport adapted to fluidly couple the therapy cavity to a source ofpositive-pressure.
 3. The system of claim 2, wherein the humidity sensorand the temperature sensor are disposed within the therapy cavityproximate the vent port.
 4. The system of claim 1, wherein the pressuresensor is disposed within the therapy cavity proximate the tissueinterface.
 5. The system of claim 1, wherein the pressure sensor, thehumidity sensor, and the temperature sensor are disposed outside thetherapy cavity.
 6. The system of claim 5, wherein the pressure sensor isdisposed proximate the negative-pressure port.
 7. The system of claim 5,wherein the humidity sensor and the temperature sensor are disposedproximate the vent port.
 8. The system of claim 1, wherein theprocessing element is disposed on an outside surface of the housing. 9.The system of claim 1, wherein the processing element is an integratedcomponent of the housing.
 10. The system of claim 1, wherein the systemfurther comprises a controller configured to receive the propertysignals from the processing element and to assess property readingsreflective of the property signals to identify the flow characteristicsof the system.
 11. The system of claim 10, wherein the processingelement further comprises a transmitter configured to transmit theproperty signals to the controller.
 12. The system of claim 10, whereinthe controller is remote from the dressing interface.
 13. The system ofclaim 10, wherein the system further comprises an instillation pumpconfigured to provide instillation fluid to the tissue interface, and asensor electrically coupled to the controller and adapted to measure aninstillation pump pressure provided by the instillation pump.
 14. Thesystem of claim 10, wherein the system further comprises an instillationpump configured to provide instillation fluid to the tissue interface,and a sensor electrically coupled to the controller and adapted tomeasure an instillation duty cycle provided by the instillation pump.15. The system of claim 10, wherein the system further comprises aninstillation pump configured to provide instillation fluid to the tissueinterface, and a sensor electrically coupled to the controller andadapted to measure an instillation pump pressure and an instillationduty cycle provided by the instillation pump.
 16. The system of claim15, wherein the controller is configured to assess the property readingsand provide an alarm identifying a blockage state condition as one ofthe flow characteristics when the instillation pump duty cycle increaseswhile the humidity remains substantially the same.
 17. The system ofclaim 16, wherein the controller is further configured to provide analarm identifying a blockage state condition when the instillationpressure increases.
 18. The system of claim 16, wherein the controlleris further configured to provide an alarm identifying a blockage statecondition when the temperature remains substantially the same.
 19. Thesystem of claim 16, wherein the system further comprises an occlusionsensor electrically coupled to the controller, wherein the controller isfurther configured to provide an alarm identifying a blockage statecondition when the occlusion sensor is tripped.
 20. The system of claim15, wherein the controller is configured to assess the property readingsand provide an alarm identifying a fluid leak state as one of the flowcharacteristics when the instillation pump duty cycle and the humidityremain substantially the same.
 21. The system of claim 20, wherein thecontroller is further configured to provide an alarm identifying a fluidleak state when the instillation pressure increases.
 22. The system ofclaim 20, wherein the controller is further configured to provide analarm identifying a fluid leak state when the temperature increases ordecreases.
 23. The system of claim 15, wherein the controller isconfigured to assess the property readings and provide an alarmidentifying a fluid leak state as one of the flow characteristics whenthe instillation pump duty cycle remains substantially the same and thehumidity increases but not to a predetermined threshold humidity. 24.The system of claim 15, wherein the controller is configured to assessthe property readings and provide an alarm identifying a dressing fillstate as one of the flow characteristics when the humidity increases toa predetermined target threshold humidity.
 25. The system of claim 24,wherein the predetermined target threshold humidity is about 90%. 26.The system of claim 24, wherein the controller is further configured toprovide an alarm identifying a dressing fill state when the temperaturedecreases.
 27. The system of claim 24, wherein the controller is furtherconfigured to provide an alarm identifying a dressing fill state whenthe wound pressure increases.
 28. The system of claim 1, wherein thedressing interface further comprises: a pH sensor mounted to the housingin fluid communication with the therapy cavity and configured to sensethe pH of the fluids adjacent the tissue interface during instillationof liquids to the tissue interface; and wherein the processing elementis electrically coupled to the pH sensor for receiving a property signalindicative of the pH, the processing element being further configured toassess the health characteristics of the tissue site.
 29. The system ofclaim 28, wherein the therapy cavity further comprises a vent portadapted to fluidly couple the therapy cavity to a source ofpositive-pressure.
 30. The system of claim 29, wherein the pH sensor isdisposed proximate the vent port.
 31. The system of claim 28, whereinthe pH sensor is disposed outside the therapy cavity.
 32. The system ofclaim 28, wherein the controller is further configured to receive theproperty signals indicative of the pH from the processing element and toassess property readings reflective of the property signals to identifythe health characteristics of the tissue site.
 33. The system of claim32, wherein the processing element is further configured to transmit theproperty signals indicative of the pH to the controller.
 34. The systemof claim 33, wherein the health characteristics of the system include awound progression state within the system, and wherein the controller isconfigured to provide an alarm indicative of the wound progression statebased on the property signals.
 35. The system of claim 34, wherein thecontroller provides an alarm indicative of the wound progression statewhen the pH increases or decreases.
 36. The system of claim 35, whereinthe controller provides an alarm indicative of the wound progressionstate when the humidity and temperature change.
 37. The system of claim35, wherein the controller provides an alarm indicative of the woundprogression state when the wound pressure is critically affected.
 38. Amethod for treating a tissue site utilizing a system for providingnegative pressure with fluid instillation therapy and assessingproperties of liquids at the tissue site, wherein the system comprises atissue interface and a dressing interface having a housing including atherapy cavity, the method comprising: disposing the tissue interface atthe tissue site, the tissue interface adapted to be coupled to a sourceof instillation fluid; disposing the therapy cavity in fluidcommunication with the tissue interface, the therapy cavity adapted tobe coupled to a source of negative pressure; providing instillationfluid from the source of instillation fluid to the therapy cavity;sensing pressure of fluids adjacent the tissue interface duringinstillation of liquids to the tissue interface using a pressure sensormounted to the housing in fluid communication with the therapy cavity;sensing humidity of fluids adjacent the tissue interface duringinstillation of liquids to the tissue interface using a humidity sensormounted to the housing in fluid communication with the therapy cavity;sensing temperature of fluids adjacent the tissue interface duringinstillation of liquids to the tissue interface using a temperaturesensor mounted to the housing in fluid communication with the therapycavity; and determining flow characteristics of the system by using aprocessing element electrically coupled to the pressure sensor, thehumidity sensor, and the temperature sensor, wherein the processingelement receives property signals indicative of the pressure, humidity,and temperature.
 39. The method of claim 38, further comprisingtransmitting the property signals to a controller within the system forassessing the flow characteristics of the system.
 40. The method ofclaim 39, further comprising receiving the property signals by thecontroller, and assessing property readings reflective of the propertysignals to identify the flow characteristics of the system.
 41. Themethod of claim 40, further comprising sensing an instillation pumppressure and an instillation duty cycle of the source of instillation,wherein the instillation pump pressure and the instillation duty cycleare provided by sensors electrically coupled to the controller.
 42. Themethod of claim 41, further comprising using the controller to assessthe property readings and provide an alarm identifying a blockage statecondition as one of the flow characteristics when the instillation pumpduty cycle increases while the humidity remains substantially the same.43. The method of claim 42, further comprising using the controller toprovide an alarm identifying a blockage state condition when theinstillation pressure increases.
 44. The method of claim 43, furthercomprising using controller to provide an alarm identifying a blockagestate condition when the temperature remains substantially the same. 45.The method of claim 43, wherein the system further comprises anocclusion sensor electrically coupled to the controller, wherein themethod further comprises using the controller to provide an alarmidentifying a blockage state condition when the occlusion sensor istripped.
 46. The method of claim 41, further comprising using thecontroller to assess the property readings and provide an alarmidentifying a fluid leak state as one of the flow characteristics whenthe instillation pump duty cycle increases and the humidity remainssubstantially the same.
 47. The method of claim 46, further comprisingusing the controller to provide an alarm identifying a fluid leak statewhen the instillation pressure increases.
 48. The method of claim 47,further comprising using the controller to provide an alarm identifyinga fluid leak state when the temperature increases or decreases.
 49. Themethod of claim 47, further comprising providing an alarm indicative ofthe fluid leak state when the wound pressure decreases.
 50. The methodof claim 41, further comprising using the controller to assess theproperty readings and provide an alarm identifying a fluid leak state asone of the flow characteristics when the instillation pump duty cycleremains substantially the same in the humidity increases but not to apredetermined threshold humidity.
 51. The method of claim 41, furthercomprising: sensing pH of fluids adjacent the tissue interface duringinstillation of liquids to the tissue interface using a pH sensormounted to the housing in fluid communication with the therapy cavity;and determining health characteristics of the tissue site by using aprocessing element electrically coupled to the pH sensor, wherein theprocessing element receives property signals indicative of the pH. 52.The method of claim 51, further comprising transmitting the propertysignals to a controller within the system for assessing the healthcharacteristics of the tissue site.
 53. The method of claim 52, furthercomprising receiving the property signals by the controller, andassessing property readings reflective of the property signals toidentify the health characteristics of the tissue site.
 54. The methodof claim 53, wherein the health characteristics of the system include awound progression state within the system, and wherein the methodfurther comprises providing an alarm indicative of the wound progressionstate based on the property signals.
 55. The method of claim 54, furthercomprising providing an alarm indicative of the wound progression statewhen the pH increases or decreases.
 56. The method of claim 55, furthercomprising providing an alarm indicative of the wound progression statewhen the humidity and temperature change.
 57. The method of claim 55,further comprising providing an alarm indicative of the woundprogression state when the wound pressure is critically affected. 58.The method of claim 55, further comprising providing an alarm indicativeof the wound progression state when the pH in the humidity increases ordecreases.
 59. The method of claim 51, further comprising logging afirst set of property readings from the pressure sensor, the humiditysensor, the temperature sensor, and the pH sensor indicative of thepressure, the humidity, the temperature, and the pH in a processingelement mounted to the housing outside the therapy cavity.
 60. Themethod of claim 51, further comprising purging fluids from the therapycavity for sensing the pressure, the humidity, temperature, and the pHof fluids at the tissue site.
 61. A method for treating a tissue siteutilizing a system for providing negative pressure with fluidinstillation therapy and assessing properties of liquids at the tissuesite, wherein the system comprises a tissue interface and a dressinginterface having a housing including a therapy cavity, comprising:providing instillation fluid from the source of instillation fluid tothe therapy cavity; sensing pressure of a first sample of fluids at thetissue site using a pressure sensor mounted to the housing in fluidcommunication with the therapy cavity; sensing humidity of a firstsample of fluids at the tissue site using a humidity sensor mounted tothe housing in fluid communication with the therapy cavity; sensingtemperature of a first sample of fluids at the tissue site using atemperature sensor mounted to the housing in fluid communication withthe therapy cavity; sensing pH of a first sample of fluids at the tissuesite using a pH sensor mounted to the housing in fluid communicationwith the therapy cavity; and purging fluids from the therapy cavityafter sensing the pressure, the humidity, temperature, and the pH of thefirst samples of fluids.